Datasheet 28L202A1B, 28L202A1A Datasheet (Philips)

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Page 1

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SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

Objective specification IC19 Data Handbook

1998 Oct 05

INTEGRATED CIRCUITS

Page 2

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

Designed for “Glueless operation in 68XXX and X86 environments”

1998 Oct 05

DESCRIPTION

The 28L202 is a high performance functional upgrade for the Philips dual channel UARTS. The SCC2692 and SC26C92 operating at 3.3 or 5 volts supply with added features and deeper partitioned FIFOs. Its configuration on power up is similar that of the SC26C92. Its differences from the SC26C92 are: 256 character receiver, 256 character transmit FIFOs, CRC error detection, 3 and 5 volt compatibility, 8 I/O ports for each UART. IRDA compatibility, arbitrating interrupt system and overall faster buss and data speeds. It is fabricated in an advanced CMOS process that allows stand by current of less that one microampere.

Pin programming will allow the device to operate with either the Motorola or Intel bus interface by changing the function of some pins. (Reset is inverted, DACKN enabled for example).

The Philips Semiconductors 28L202 Dual Universal Asynchronous Receiver/Transmitter (DUART) is a single-chip CMOS–LSI communications device that provides two full-duplex asynchronous receiver/transmitter channels in a single package. It interfaces directly with microprocessors and may be used in a polled or interrupt driven system.

The operating mode and data format of each channel can be programmed independently. Additionally, each receiver and transmitter can select its operating speed as one of twenty-three fixed baud rates; a 16X clock derived from a programmable counter/timer, or an external 1X or 16X clock. The baud rate generator and counter/timer can operate directly from a crystal or from external clock inputs. The ability to independently program the operating speed of the receiver and transmitter make the DUART particularly attractive for dual-speed channel applications such as clustered terminal systems.

Each receiver and transmitter is buffered by eight character FIFOs to minimize the potential of receiver overrun, transmitter underrun and to reduce interrupt overhead in interrupt driven systems. In addition, a flow control capability is provided to disable a remote transmitter when the receiver buffer is full.

Also provided on the 28L202 are a multipurpose 7-bit input port and a multipurpose 8-bit output port. These can be used as general-purpose I/O ports or can be assigned specific functions (such as clock inputs or status/interrupt outputs) under program control.

The 28L202 are available in two package versions: a 44-pin PLCC and 44-pin plastic quad flat pack (PQFP).

FEA TURES

•3.3 or 5.0 volt operation

•Dual full-duplex independent asynchronous receiver/transmitters

•256 or larger character FIFOs for each receiver and transmitter

•Power up as 8 bit data no parity one stop bit 9600 baud

•Pin programming (PQFP package) to 68K or 80xxx bus interface

•Programmable data format

– 5 to 8 data bits plus parity

– Odd, even, no parity or force parity – 1, 1.5 or 2 stop bits programmable in 1/16-bit increments

•16-bit programmable Counter/Timer

•Programmable baud rate for each receiver and transmitter

selectable from:

– 23 fixed rates: 50 to 230.4k baud – Other baud rates to MHz at 16X – Programmable user-defined rates derived from a

programmable Counter/timer

– External 1X or 16X clock

•Parity, framing, and overrun error detection

•False start bit detection

•Line break detection and generation

•Programmable channel mode

– Normal (full-duplex) – Automatic echo – Local loop back – Remote loop back – Multi-drop mode (also called ‘wake-up’ or ‘9-bit’)

•Multi-function 7-bit input port

– Can serve as clock or control inputs – Change of state detection on eight inputs – Inputs have typically >100k pull-up resistors

•Multi-function 8-bit output port

– Individual bit set/reset capability – Outputs can be programmed to be status/interrupt signals

•Versatile interrupt system

– Single interrupt output with eight maskable interrupting

conditions

– Output port can be configured to provide a total of up to six

separate interrupt outputs that may be wire ORed.

– Each FIFO can be programmed for four different interrupt

levels.

– Watch dog timer for each receiver

•Maximum data transfer rates:

– 1X – 1Mb/sec, 16X – 1Mb/sec

•Automatic wake-up mode for multi-drop applications

•Start-end break interrupt/status

•Detects break which originates in the middle of a character

•On-chip crystal oscillator

•Power down mode

•Receiver time-out mode

•Single +3.3V or +5V power supply

•Powers up to emulate SCC2692 and SC26C92

Page 3

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

ORDERING INFORMATION

ББББББББББББ

DESCRIPTION

БББББББББ

INDUSTRIAL

= +3.3 +5V ±10%,

= –40 TO +85C

БББББББББ

DRAWING NUMBER

44-Pin Plastic Leaded Chip Carrier (PLCC)

28L202A1A

SOT187–2

44-Pin Plastic Quad Flat Pack (PQFP)

28L202A1B

SOT307–2

Page 4

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

PIN CONFIGURATION DIAGRAM

PIN FUNCTION PIN FUNCTION

1NC 27D2 2A0 28D0 3 I/OB3 29 I/OA6 4 A1 30 I/OA4 5 I/OB1 31 I/OA2 6 A2 32 I/OA0 7 A3 33 TxDA 8 I/OB0 34 NC 9 WRN 35 RxDA 10 RDN 36 X1/CLK 11 RxDB 37 X2 12 I/M 38 RESET 13 TxDB 39 CEN 14 I/OA1 40 I/OB2 15 I/OA3 41 I/OB6 16 I/OA5 42 I/OB5 17 I/OA7 43 I/OB4 18 D1 44 V

19 D3 45 A4 20 D5 46 A5 21 D7 47 I/OB7 22 V

48 PRE

23 NC 49 V

24 INTRN 50 V

25 D6 51 NC 26 D4 52 NC

PLCC

TOP VIEW

INDEX

CORNER

SD00680

Page 5

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

PIN CONFIGURATION DIAGRAM

PIN FUNCTION PIN FUNCTION

1NC 27D2 2A0 28D0 3 I/OB3 29 I/OA6 4 A1 30 I/OA4 5 I/OB1 31 I/OA2 6 A2 32 I/OA0 7 A3 33 TxDA 8 I/OB0 34 NC 9 R/WN 35 RxDA 10 DACKN 36 X1/CLK 11 RxDB 37 X2 12 I/M 38 RESETN 13 TxDB 39 CEN 14 I/OA1 40 I/OB2 15 I/OA3 41 IACKN 16 I/OA5 42 I/OB5 17 I/OA7 43 I/OB4 18 D1 44 V

19 D3 45 A4 20 D5 46 A5 21 D7 47 I/OB7 22 V

48 PRE

23 NC 49 V

24 INTRN 50 V

25 D6 51 NC 26 D4 52 NC

PLCC

TOP VIEW

INDEX

CORNER

SD00681

Page 6

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

ABSOLUTE MAXIMUM RATINGS

SYMBOL

PARAMETER

RATING

БББББ

UNIT

Operating ambient temperature range

See Note 3

БББББ

C

TSTG

Storage temperature range

–65 to +150

БББББ

C

Voltage from VCC to GND

–0.5 to +7.0

БББББ

Voltage from any pin to GND

–0.5 to VCC + 0.5

БББББ

PD5

Power Dissipation at VCC = 5.6 Volts

БББББ

PD3

Power Dissipation at VCC = 3.3 Volts

0.5

БББББ

NOTES:

1. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and the functional operation of the device at these or any other conditions above those indicated in the. Operation Section of this specification is not implied.

2. For operating at elevated temperatures, the device must be derated based on +150C maximum junction temperature.

3. Parameters are valid over specified temperature range. See ordering information table for applicable temperature range and operating supply range.

4. This product includes circuitry specifically designed for the protection of its internal devices from damaging effects of excessive static charge. Nonetheless, it is suggested that conventional precautions be taken to avoid applying any voltages larger than the rated maxim.

Page 7

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

D0–D7

RDN

WRN

CEN

A0–A5

RESET

INTRN

X1/CLK

BUS BUFFER

OPERATION CONTROL

ADDRESS

DECODE

R/W CONTROL

INTERRUPT CONTROL

IMR ISR

TIMING

BAUD RATE

GENERATOR

CLOCK

SELECTORS

COUNTER/

TIMER

XTAL OSC

CSRA

CSRB

ACR

CTLR

CHANNEL A

TRANSMIT

HOLDING REG

TRANSMIT

SHIFT REGISTER

RECEIVE

HOLDING REG (3)

RECEIVE

SHIFT REGISTER

MRA1, 2

CRA SRA

I/O PORT A

CHANGE OF

STATE

DETECTORS (4)

I/O PORT B

FUNCTION

SELECT LOGIC

OPCR

TxDA

RxDA

I/O7:0A

I/O7:0B

GND

CONTROL

TIMING

INTERNAL DATABUS

CHANNEL B (AS ABOVE)

IPCR

ACR

OPR

CTLR

RxDB

TxDB

SD00679

FIFO RAM

FIFO DATABUS

FIFO

CONTROL

I/M

Figure 1. Block Diagram

Page 8

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

PIN CONFIGURATION FOR 80XXX BUS INTERFACE (INTEL)

ÁÁ

SYMBOL

TYPE

БББББББББББББББББББББББББББ

NAME AND FUNCTION

I/M

Bus Configuration: When high or not connected configures the bus interface to the Conditions shown in this table.

D0–D7

I/O

Data Bus: Bi-directional 3-State data bus used to transfer commands, data and status between the DUART and the CPU. D0 is the least significant bit.

ÁÁ

CEN

БББББББББББББББББББББББББББ

Chip Enable: Active-Low input signal. When Low, data transfers between the CPU and the DUART are enabled on D0–D7 as controlled by the WRN, RDN and A0–A3 inputs. When High, places the D0–D7 lines in the 3-State condition.

WRN

Write Strobe: When Low and CEN is also Low, the contents of the data bus is loaded into the addressed register. The transfer occurs on the rising edge of the signal.

ÁÁ

RDN

БББББББББББББББББББББББББББ

Read Strobe: When Low and CEN is also Low, causes the contents of the addressed register to be presented on the data bus. The read cycle begins on the falling edge of RDN.

A0–A3

Address Inputs: Select the DUART internal registers and ports for read/write operations.

ÁÁ

RESET

БББББББББББББББББББББББББББ

Reset: A High level clears internal registers (SRA, SRB, IMR, ISR, OPR, OPCR), puts OP0 – OP7 in the High state, stops the counter/timer, and puts Channels A and B in the inactive state, with the TxDA and TxDB outputs in the mark (High) state. Sets MR pointer to MR1.

INTRN

Interrupt Request: Active-Low, open-drain, output which signals the CPU that one or more of the eight maskable interrupting conditions are true.

ÁÁ

X1/CLK

БББББББББББББББББББББББББББ

Crystal 1: Crystal or external clock input. A crystal or clock of the specified limits must be supplied at all times. When a crystal is used, a capacitor must be connected from this pin to ground (see Figure 7).

ÁÁ

БББББББББББББББББББББББББББ

Crystal 2: Connection for other side of the crystal. When a crystal is used, a capacitor must be connected from this pin to ground (see Figure 7). If X1/CLK is driven from an external source, this pin must be left open.

RxDA

Channel A Receiver Serial Data Input: The least significant bit is received first. “Mark” is High; “space” is Low.

RxDB

Channel B Receiver Serial Data Input: The least significant bit is received first. “Mark” is High; “space” is Low.

ÁÁ

TxDA

БББББББББББББББББББББББББББ

Channel A Transmitter Serial Data Output: The least significant bit is transmitted first. This output is held in the “mark” condition when the transmitter is disabled, idle or when operating in local loop back mode. “Mark” is High; “space” is Low.

ÁÁ

TxDB

БББББББББББББББББББББББББББ

Channel B Transmitter Serial Data Output: The least significant bit is transmitted first. This output is held in the ‘mark’ condition when the transmitter is disabled, idle, or when operating in local loop back mode. ‘Mark’ is High; ‘space’ is Low.

ÁÁ

I/O[7:0]A

БББББББББББББББББББББББББББ

General-purpose input and output ports channel A: The character of these pins is controlled by I/OPCR. They may be inputs or outputs and will present many internal clocks and interrupt signals: RTS, CTS, DTR, DSR etc. All have change of state detectors and the input is always active.

ÁÁ

I/O[7:0}B

БББББББББББББББББББББББББББ

General-purpose input and output ports channel B: The character of these pins is controlled by I/OPCR. They may be inputs or outputs and will present many internal clocks and interrupt signals: RTS, CTS, DTR, DSR etc. All have change of state detectors and the input is always active.

Pwr

Power Supply: +3.3 or +5V supply input 10%

GND

Pwr

Ground

Page 9

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

PIN CONFIGURATION FOR 68XXX BUS INTERFACE (INTEL)

ÁÁ

SYMBOL

TYPE

БББББББББББББББББББББББББББ

NAME AND FUNCTION

I/M

Bus Configuration: When low configures the bus interface to the Conditions shown in this table.

D0–D7

I/O

Data Bus: Bi-directional 3-State data bus used to transfer commands, data and status between the DUART and the CPU. D0 is the least significant bit.

ÁÁ

CSN

БББББББББББББББББББББББББББ

Chip Enable: Active-Low input signal. When Low, data transfers between the CPU and the DUART are enabled on D0–D7 as controlled by the R/WN and A0–A3 inputs. When High, places the D0–D7 lines in the 3-State condition.

R/WN

Read/Write: Input Signal. When CSN is low R/WN high input a read cycle, when low a write cycle.

ÁÁ

IACKN

БББББББББББББББББББББББББББ

Interrupt Acknowledge: Active low input indicates an interrupt acknowledge cycle. Usually asserted by the CPU in response to an interrupt request. When asserted places the interrupt vector on the bus and asserts DACKN.

DACKN

Data Transfer Acknowledge: A3–State active –low output asserted in a write, read, or interrupt acknowledge cycle to indicate proper transfer of data between the CPU and the DUART.

A0–A3

Address Inputs: Select the DUART internal registers and ports for read/write operations.

ÁÁ

RESETN

БББББББББББББББББББББББББББ

Reset: A low level clears internal registers (SRA, SRB, IMR, ISR, OPR, OPCR), puts OP0–OP7 in the High state, stops the counter/timer, and puts Channels A and B in the inactive state, with the TxDA and TxDB outputs in the mark (High) state. Sets MR pointer to MR1.

ÁÁ

INTRN

БББББББББББББББББББББББББББ

Interrupt Request: Active–Low, open-drain, output which signals the CPU that one or more of the eight maskable interrupting conditions are true.

X1/CLK

ÁÁ

БББББББББББББББББББББББББББ

RxDA

Channel A Receiver Serial Data Input: The least significant bit is received first. “Mark” is High; “space” is Low.

RxDB

Channel B Receiver Serial Data Input: The least significant bit is received first. “Mark” is High; “space” is Low.

ÁÁ

TxDA

БББББББББББББББББББББББББББ

ÁÁ

TxDB

БББББББББББББББББББББББББББ

ÁÁ

I/O[7:0]A

I/O

БББББББББББББББББББББББББББ

ÁÁ

I/O[7:0]B

I/O

БББББББББББББББББББББББББББ

Power

Power Supply: +3.3 or +5V supply input 10%

Power

Ground

Page 10

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

AC CHARACTERISTICS

1, 2, 3

LIMITS

SYMBOL

PARAMETER

MIN

TYP

MAX

ÁÁÁ

UNIT

Reset timing (See Figure 2)

RES

Reset Pulse Width

200

ÁÁÁ

Bus Timing5 (See Figure 3)

A0–A3 setup time to RDN, WRN Low

ÁÁÁ

A0–A3 hold time from RDN, WRN low

CEN setup time to RDN, WRN low

ÁÁÁ

CEN Hold time from RDN WRN low

ÁÁÁ

WRN, RDN pulse width (Low time)

110

Data valid after RDN low

ÁÁÁ

RDN low to data bus active

ÁÁÁ

Data bus floating after RDN or CEN high

ÁÁÁ

RDN or CEN high to data bus invalid

Data bus setup time before WRN or CEN high (write cycle)

ÁÁÁ

Data hold time after WRN high

ÁÁÁ

RWD

High time between read and/or write cycles

1, 7

Port Timing1 (See Figure 5)

Port in setup time before RDN low (Read IP ports cycle)

ÁÁÁ

Port in hold time after RDN high

OP port valid after WRN or CEN high (OPR write cycle)

110

ÁÁÁ

Interrupt Timing (See Figure 6)

INTRN (or OP3–OP7 when used as interrupts) negated from:

ÁÁÁ

Read RxFIFO (RxRDY/FFULL interrupt)

100

Write TxFIFO (TxRDY interrupt)

100

ÁÁÁ

Reset Command (delta break change interrupt)

100

ÁÁÁ

Stop C/T command (Counter/timer interrupt)

100

Read IPCR (delta input port change interrupt)

100

ÁÁÁ

Write IMR (Clear of change interrupt mask bit(s))

100

ÁÁÁ

Clock Timing (See Figure 7)

CLK

X1/CLK high or low time

ÁÁÁ

CLK

X1/CLK frequency

0.1

3.686

ÁÁÁ

MHz

CTC

C/T Clk (IP2) high or low time (C/T external clock input)

ÁÁÁ

CTC

C/T Clk (IP2) frequency

MHz

RxC high or low time (16X)

ÁÁÁ

RxC Frequency (16X)

ÁÁÁ

MHz

RxC Frequency (1x)

4, 9

MHz

TxC High or low time (16X)

ÁÁÁ

TxC frequency (16X)

ÁÁÁ

MHz

TxC frequency (1X)

4, 5

ÁÁÁ

MHz

Transmitter Timing (See Figure 8)

TXD

TxD output delay from TxC low (TxC input pin)

120

ÁÁÁ

TCS

Output delay from TxC output pin low to TxD data output

–30

ÁÁÁ

Receiver Timing (See Figure 9)

RXS

RxD data setup time to RxC high

100

ÁÁÁ

RXH

RxD data hold time from RxC high

100

ÁÁÁ

NOTES:

1. Parameters are valid over specified temperature range.

2. All voltage measurements are referenced to ground (GND). For testing, all inputs swing between 0.4 V and 3.0 V with a transition time of 5 ns maximum. For X1/CLK this swing is between 0.4 V and 4.4 V . All time measurements are referenced at input voltage of 0.8 V and

2.0 V and output voltages of 0.8 V and 2.0 V , as appropriate.

3. Test conditions for outputs; C

= 150 pF, except interrupt outputs. Test conditions for interrupt outputs; CL = 50 pF, RL = 2.7 Kohm to VCC.

4. Typical values are at +25C, typical supply voltages, and typical processing parameters.

5. Timing is illustrated and referenced to the WRN and RDN inputs. Also, CEN may be the “strobing” input. CEN and RDN (also CEN and WRN) are ORed internally. The signal asserted last initiates the cycle and the signal negated first terminates the cycle.

6. Guaranteed by characterization of sample units.

7. If CEN is used as the “strobing” input, the parameter defines the minimum high times between one CEN and the next. The RDN signal must be negated for t

RWD

to guarantee that any status register changes are valid.

8. Minimum frequencies are not tested but are guaranteed by design.

9. Clocks for 1X mode should be symmetrical.

Page 11

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

OVER ALL DESCRIPTION

The SC28L202 is composed of several functional blocks. They are listed in the approximate order of hierarchy as seen from the pins of the device.

•Timing Circuits

•Bus interface. 68K or x86 format

•I/O Ports

•UARTS

•Arbitrating Interrupt Structure

•Character & Address Recognition

•Variable FIFO Partition Structure

•Test Modes and Boundary Scan

BRIEF DESCRIPTION OF FUNCTIONAL BLOCKS Timing Circuits

Crystal Oscillator

The crystal oscillator is the main timing element for the 28L202. It is nominally set at 14.7456 MHz and may be used to 29.4912 MHz. The use of an external clock allows all frequencies to 40 MHz.

BRG

The BRG is the baud rate generator, is driven by the crystal input and generated all of the 24 “fixed” internal baud rates.

Counter-Timer .

The counter-timer provides miscellaneous baud rated, timing periods and acts as an extra watchdog timer for the for the receivers. It has 8 clock sources.

Bus Interface

The bus interface operates in “68K” or “x86” format as selected by the I/M pin. The signals used by this section are the Address, Data bus, Chip select, read/write, Data acknowledge and Interrupt acknowledge and Interrupt request. Assertion of DACKN requires two edges of the X1clk after the assertion of CEN.

I/O ports

Each UART is provided with 8 I/O ports. Each port is equipped with a change of state detector. The input circuit of these pins is always active. Under program control the ports my display internal signals or static logic levels. The functions represented by the I/O ports include hardware flow control. Modem signals, signals for interrupt conditions or various internal clocks and timing intervals. Noisy inputs to the I/O ports are filtered (de-bounced) by a 38.4 KHz clock.

UARTS

The uarts are fully independent, full duplex and provide all normal asynchronous functions: 5 to 8 data bits, parity odd or even, programmable stop bit length, false start bit detection. Also provided are 256 byte FIFOs Xon/Xoff software flow control and IRDA pulse modulation. The BRG, Counter-timer, or external clocks provide the baud rates. The receivers and transmitters may operate in either the “1x” or “16x” modes.

Interrupt Arbitration

The interrupt system uses a highly programmable arbitrating technique to establish when an interrupt should be presented to the processor. The advantageous feature of this system is the

presentation of the context of the interrupt. It is presented in both a current interrupt register and in the interrupt vector. The context of the interrupt shows the interrupting channel, identifies which of the 8 possible sources in requesting interrupt service and in the case of a receiver or transmitter gives the current fill level of the FIFO.

The content of the current interrupt register also drives the Global Registers of the interrupt system. These registers are indirect addresses (pointers) to the fields describing the internal source requesting interrupt service.

Programming of Bid Control Registers allows the interrupt level of any source to be varied at any time over a range of 256 levels.

Character and Address Recognition

The character recognition system is designed as a general system. There is one for each UART. Each recognition block stores up to three characters. The recognition is done on a byte boundary and sets status and interrupt when an recognition event occurs. Each has four modes of operation.

A subset of the recognition system is Xon/Xoff character recognition and multi-drop address recognition. If Xon/Xoff or multi-dorp function is enabled the recognition system passes the information about the recognition event to the appropriate receiver or transmitter state machine for execution. In any case the information about a recognition event is available to the interrupt system and to the control processor.

FIFO Partitioning and Control

The FIFO memory is implemented in ram. Nominally 1000 bytes of ram are divided between the four FIFOs of the DUART. The default partition is 256 (0xFF) bytes for each fifo. Under program control size of the partition for any a particular FIFO may be varied from 1 to

1024. The interrupt level for each FIFO is also under program control and

is continuously variable through out the range of the partition. A small processor controls all of the FIFO reading, writing, interrupting, flow control signaling, and status reporting.

Test Modes

Three test modes are provided to verify UART function and processor interface integrity . These are Auto echo, Local Loop Back, and Remote Loop Back. Through local loop back the software developer may verify all of the interrupt, flow control; the hardware designer verifies all of the timing and pin connections. This information is obtained without any recourse to external test equipment or terminals.

Boundary scan provides verification of manufacturing process and to a lesser extent identifies damage that may occur to pins due to electrical over stress or electrostatic discharge.

DET AILED DESCRIPTIONS

NOTE: For the convenience of the reader some paragraphs in the

following section will be repeated in descriptions of closely linked functions.

Timing Circuits

Crystal Oscillator

The crystal oscillator operates directly from a crystal, tuned between

14.7456 MHz and 29 4912 MHz connected across the X1/CCLK and X2 inputs with a minimum of external components. BRG values listed for the clock select registers correspond to a 14.7456 MHz

Page 12

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

crystal frequency. Use of different frequencies will change the “standard” baud rates by precisely the ratio of 14.7456 to the different crystal.

An external clock up to 40 MHz frequency range may be connected to X1/CCLK. If an external clock is used instead of a crystal, X1/CCLK must be driven and X2 left floating. The X1 clock serves as the basic timing reference for the baud rate generator (BRG) and is available to the BRG timers, counter-timers, and control logic.

Baud Rate Generator BRG

The baud rate generator operates from the oscillator or external X1/CCLK clock input and generates 24 commonly used data communications baud rates (including MIDDI) ranging from 50 to

230.4K baud. These common rates may be doubled (up to 460.8

and 1500K baud) when faster clocks are used on the X1/X2 clock inputs. (See Receiver and Transmitter Clock Select Register descriptions.) All of these are available simultaneously for use by any receiver or transmitter. The clock outputs from the BRG are at 16X the actual baud rate.

Counter-Timer

The two Counter/Timers are programmable 16 bit dividers that are used for generating miscellaneous clocks or generating timeout periods. These clocks may be used by any or all of the receivers and transmitters in the DUART or may be directed to an I/O pin for external use.

Counter/Timer programming

The counter timer is a 16-bit programmable divider that operates in one of five modes: character count, pulse mode, counter, timer, and time out. Character count counts characters. The pulse mode generates a periodic pulse of one clock period in width. The timer mode it generates a square wave. In the counter mode it generates a time delay. In the time out mode it monitors the time between received characters. The C/T uses the numbers loaded into the Counter/Timer Lower Register (CTLR) and the Counter/T imer Upper Register (CTUR) as its divisor. The counter timer is controlled with six commands: Start/Stop C/T, Read/Write Counter/Timer lower register and Read/Write Counter/Timer upper register. These commands have slight differences depending on the mode of operation. Please see the detail of the commands under the CTLR/CTUR Register descriptions.

When ever the these timers are selected via the receiver or transmitter Clock Select register their output will be configured as a 16x clock for the respective receiver or transmitter. Therefore one needs to program the timers to generate a clock 16 times faster than the data rate. The formula for calculating ’n’, the number loaded to the CTUR and CTLT registers.

For the timer mode the formula is as follows:

n 



Brg timer input frequency

2  16  Baud rate desired



–1

For the pulse mode the formula is as follows:

n 



Brg timer input frequency

16  Baud rate desired



–1

Note: ‘n’ may assume values of 0 and 1. In previous Philips data communications controllers these values were not allowed. The counter/timer control register (CTCR) controls the BRG timer input frequency.

The frequency generated from the above formula will be at a rate 16 times faster than the desired baud rate. The transmitter and receiver state machines include divide by 16 circuits, which provide the final frequency and provide various timing edges used in the qualifying the serial data bit stream. Often this division will result in a non-integer value: 26.3 for example. One may only program integer numbers to a digital divider . There for 26 would be chosen. If 26.7 were the result of the division then 27 would be chosen. This gives a baud rate error of 0.3/26.3 or 0.3/26.7 that yields a percentage error of 1.14% or 1.12% respectively, well within the ability of the asynchronous mode of operation. Higher input frequency to the counter reduces the error effect of the fractional division.

One should be cautious about the assumed benign effects of small errors since the other receiver or transmitter with which one is

communicating may also have a small error in the precise baud rate.

In a “clean” communications environment using one start bit, eight data bits and one stop bit the total difference allowed between the transmitter and receiver frequency is approximately 4.6%. Less than eight data bits will increase this percentage.

Bus Interface

The bus interface operates in two modes selected by the I/M pin. If this pin is high or left open the signals DACKN signal is not generated or used and data flow to and from the chip is controlled by the state the CEN, RDN, WRN pin combination. If the I/M pin is tied low the data is written to the device when the DACKN pin is asserted low by the DUART. Read data is presented by a delay from CEN active.

The Host interface is comprised of the signal pins CEN, WRN RDN, (or R/WN) IACKN, DACKN, IRQN, 6 address pins and 8 three-state data bus pins.

Addressing of the various functions of the DUART is through the address bus A (5:0). Data is presented on the 8-bit data bus.

DACKN Cycle

When operating in the “68K” mode bus cycle completion is indicated by the DACKN pin (an open drain signal) going low. This occurs two X1 clock edges after the cycle begins. Usually in this mode the address and data are set up with respect to the leading edges of the bus cycle.

When operating in the “x86” mode DACKN is not generated. Data is written on the termination of CEN or WRN which ever one occurs first. Read data is presented from the leading edge of the read condition; CEN and RDN both low.

IACKN Cycle, Update CIR

When the host CPU responds to the interrupt, it will usually assert the IACKN signal low. This will cause the DUART to generate an IACKN cycle in which the condition of the interrupting device is determined. When IACKN asserts, the last valid interrupt number is captured in the CIR. The value captured presents all of the important details of the highest priority interrupt at the moment the IACKN (or the “Update CIR” command) was asserted. Due to system interrupt latency, the interrupt condition captured by the CIR may not be the condition that caused the initial assertion of the interrupt.

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1998 Oct 05

interrupting channel. This allows the interrupt vector to steer the interrupt service directly to the proper service routine. The interrupt value captured in the CIR remains until another IACKN cycle occurs or until an “Update CIR” command is given to the DUART. The interrupting channel and interrupt type fields of the CIR set the current “interrupt context” of the DUART. The channel component of the interrupt context allows the use of Global Interrupt Information registers that appear at fixed positions in the register address map. For example, a read of the Global RxFIFO will read the channel B RxFIFO if the CIR interrupt context is channel B receiver. At another time read of the GRxFIFO may read the channel A RxFIFO (CIR holds a channel A receiver interrupt) and so on. Global registers exist to facilitate qualifying the interrupt parameters and for writing to and reading from FIFOs without explicitly addressing them.

The CIR will load with 0x’00 if IACKN or Update CIR is asserted when the arbitration circuit is NOT asserting an interrupt. In this condition there is no arbitration value that exceeds the threshold value. When Interrupt vector modification is active in this situation the interrupt vector bits associated with the CIR will all be zero.

I/O Ports

Eight I/O ports are provided for each channel. They may be programmed to be inputs or outputs. The input circuits are always active whether programmed as and input or an output. A 2 bit code controls what function these pins will present. Most I/O ports default to high impedance input state on power up. Those pins used for modem control (RTS, DTR) will set to output high unless the PRE pin is tied low.

Input Characteristics

Eight I/O pins are provided for each channel. These pins are configured individually to be inputs or outputs. As inputs they may be used to bring external data to the bus, as clocks for internal functions or external control signals. Each I/O pin has a “Change of State” detector. The change detectors are used to signal a change in the signal level at the pin (Either 0 to 1 or 1 to 0 transitions). The level change on these pins must be stable for 25 to 50 us (two edges of the 38.4 KHz baud rate clock) before the detectors will signal a valid change. These are typically used for interface signals from modems to the DUART and from there to the host.

Output Port

The OPR, OPCR, MR, and CR registers may control the I/O pins when configured as outputs. Via appropriate programming the pins of the output port may be configures as another parallel port to external circuits, or they may represent internal conditions of the UART. When this 8-bit port is used as a general-purpose output port, the output port pins drive a state that is the complement of the Output Port Register (OPR). The OPR register is set and reset by writing to the SOPR and ROPR addresses. (See the description of the SOPR and ROPR registers). The output pins will drive the inverse data polarity of the OPR registers. The OPCR register conditions these output pins to be controlled by the OPR or by other signals in the chip. Output ports are driven high on hardware reset.

UART Operation

Receiver and Transmitter

The Dual UART has two full duplex asynchronous receiver/transmitters. The operating frequency for the receiver and transmitter can be selected independently from the baud rate generator, the counter, or from an external input. Registers that are central to basic full-duplex operation are the mode registers (MR0, MR1 and MR2), the clock select registers (RxCSR and TxCSR), the

command register (CR), the status register (SR), the transmit holding register (TxFIFO), the receive holding register (RxFIFO) interrupt status register (ISR) and interrupt mask register (IMR).

Transmitter Status Bits

The SR (Status Register, one per UART) contains two bits that show the condition of the transmitter FIFO. These bits are TxRDY and TxEMT. TxRDY means the TxFIFO has space available for one or more bytes; TxEMT means The TxFIFO is completely empty and the last stop bit has been completed. TxEMT can not be active without TxRDY also being active. These two bits will go active upon initial enabling of the transmitter. They will extinguish on the disable or reset of the transmitter.

Transmission resumes and the TxEMT bit is cleared when the CPU loads at least one new character into the TxFIFO. The TxRDY will not extinguish until the TxFIFO is completely full. The TxRDY bit will always be active when the transmitter is enabled and there is at lease one open position in the TxFIFO.

The transmitter is disabled by a hardware reset, a transmitter reset in the command register or by the transmitter disable bit also in the command register (CR). The transmitter must be explicitly enabled via the CR before transmission can begin. Note that characters cannot be loaded into the TxFIFO while the transmitter is disabled, hence it is necessary to enable the transmitter and then load the TxFIFO. It is not possible to load the TxFIFO and then enable the transmission.

Note the difference between transmitter disable and transmitter reset.

Either hardware or software may cause the reset action. When reset the transmitter stops transmission immediately. The transmit data output will be driven high, transmitter status bits set to zero and any data remaining in the TxFIFO will be discarded.

The transmitter disable is controlled by the Tx Enable bit in the command register. Setting this bit to zero will not stop the transmitter immediately but will allow it to complete any tasks presently underway . It is only when the last character in the TxFIFO and its stop bit(s) have been transmitted that the transmitter will go to its disabled state. While the transmitter enable/disable bit in the command register is at zero the TxFIFO will not accept any more characters.

Transmission of “break”

Transmission of a break character is often needed as a synchronizing condition in a data stream. The “break” is defined as a start bit followed by all zero data bits by a zero parity bit (if parity is enabled) and a zero in the stop bit position. The forgoing is the minimum time to define a break. The transmitter can be forced to send a break (continuous low condition) by issuing a start break command via the CR. This command does not have any timing associated with it. Once issued the TxD output will be driven low (the spacing condition) and remain there until the host issues a command to “stop break” via the CR or the transmitter is issued a software or hardware reset. In normal operation the break is usually much longer than one character time.

1x and 16x modes, Transmitter

The transmitter clocking has two modes: 16x and 1x. Data is always sent at the 1x rate. However the logic of the transmitter may be operated with a clock that is 16 times faster than the data rate or at the same rate as the data i.e. 1x. All clocks selected internally for the transmitter (and the receiver) will be 16x clocks. Only when an

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Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

external clock is selected may the transmitter logic and state machine operate in the 1x mode. The 1x or 16x clocking makes little difference in transmitter operation. (This is not true in the receiver) In the 16X-clock mode the transmitter will recognize a byte in the TxFIFO within 1/16 to 2/16-bit time and thus begin transmission of the start bit. In the 1x mode this delay may be up to 2 bit times.

Transmitter FIFO

The FIFO configuration of the as 28L202 is not fixed in size. The dimension of each FIFO is under program control and may set from a value of 1 byte to 1021. It is designed to facilitate large data blocks and to provide very flexible interrupt for each FIFO. Interrupt levels may be set to any level within the FIFO size and may be set differently for each FIFO. Logic associated with the FIFO encodes the number of filled positions for presentation to the interrupt arbitration system. The encoding is always 1 less than the number of filled positions. Thus, a full RxFIFO will bid with the value or 255; when empty it will not bit at all; one position occupied bids with the value 0. An empty FIFO will not bid since no character is available. Normally RxFIFO will present a bid to the arbitration system whenever it has one or more filled positions. The MR2 [3:2 bits allow the user to modify this characteristic so that bidding will not start until one of four levels (one or more filled, 1/2 filled, 3/4 filled, full) have been reached. As will be shown later this feature may be used to make slight improvements in the interrupt service efficiency . A similar system exists in the transmitter.

The FIFO is controlled by three parameters: size, interrupt level and page size. The hardware reset establishes the FIFO size for each receiver and transmitter at 256 bytes, the interrupt level at 128 bytes, and the page size 0. The internal FIFO control unit manages the FIFO loading, addressing, empty-full status and current fill level. It also notifies the RTS/CTS Xon/Xoff circuits when the FIFO levels have reached the appropriate fill levels to trigger their corresponding actions.

Transmitter

The 28L202 is conditioned to transmit data when the transmitter is enabled through the command register. The transmitter of the 28L202 indicates to the CPU that it is ready to accept a character by setting the TxRDY bit in the status register. This condition can be programmed to generate an interrupt request at I/O6 or I/O7 and INTRN. When the transmitter is initially enabled the TxRDY and TxEMPT bits will be set in the status register. When a character is loaded to the transmit FIFO the TxEMPT bit will be reset. The TxEMPT bit will not set until the transmit FIFO is empty and the transmit shift register has finished transmitting the stop bit of the last character written to the transmit FIFO, or the transmitter is disabled and then re-enabled.

The TxRDY bit is set whenever the transmitter is enabled and the TxFIFO is not full. Data is transferred from the holding register to transmit shift register when it is idle or has completed transmission of the previous character. Characters cannot be loaded into the TxFIFO while the transmitter is disabled.

The transmitter converts the parallel data from the CPU to a serial bit stream on the TxD output pin. It automatically sends a start bit followed by the programmed number of data bits, an optional parity bit, and the programmed number of stop bits. The least significant bit is sent first. Following the transmission of the stop bits, if a new character is not available in the TxFIFO, the TxD output remains High and the TxEMT bit in the Status Register (SR) will be set to 1. Transmission resumes and the TxEMT bit is cleared when the CPU loads a new character into the TxFIFO.

If the transmitter is disabled, it continues operating until the character currently being transmitted is completely sent out. The transmitter can be forced to send a continuous Low condition by issuing a send break command. The transmitter can be reset through a software command. If it is reset, operation ceases immediately and the transmitter must be enabled through the command register before resuming operation.

If CTS option is enabled (MR2 [4] = 1), the CTS input at I/O0 or I/O1 must be Low in order for the character to be transmitted. The transmitter will check the state of the CTS input at the beginning of each character transmitted. If it is found to be High, the transmitter will delay the transmission of any following characters until the CTS has returned to the low state. CTS going high during the serialization of a character will not affect that character.

The transmitter can also control the RTSN outputs, I/O0 or I/O1 via MR2 [5]. When this mode of operation is set the meaning of the I/O0 or I/O1 signals is “all bytes loaded to the transmitter’s FIFO have been transmitted including the last stop bit(s).

Receiver Operation

Receiver

The receiver accepts serial data on the RxD pin, converts the serial input to parallel format, checks for start bit, stop bit, parity bit (if any), framing error or break condition, and presents the assembled character and its status condition to the CPU via the RxFIFO. Three status bits are FIFOed with each character received. The RxFIFO is really 11 bits wide: eight data and 3 status. Unused FIFO bits for character lengths less than 8 bits are set to zero. It is important to note that receiver logic considers the entire message to be contained within the start bit to the stop bit. It is not aware that a message may contain many characters. The receiver returns to its idle mode at the end of each stop bit! As described below it immediately begins to search for another start bit, which is normally, of course, immediately forth coming.

1x and 16x mode, Receiver

The receiver operates in one of two modes: 1x and 16x. Of the two, the 16x is more robust and the preferred mode. Although the 1x mode may allow a faster data rate is does not provide for the alignment of the receiver 1x data clock to that of the transmitter. This strongly implies that the 1x clock of the remote transmitter is available to the receiver; the two devices are physically close to each other.

The 16x mode operates the receiver logic at a rate 16 times faster than the 1x data rate. This allows for validation of the start bit, validation of level changes at the receiver serial data input (RxD), and a stop bit length as short as 9/16 bit time. Of most importance in the 16x mode is the ability of the receiver logic to align the phase of the receiver 1x data clock to that of the transmitter with an accuracy of less than 1/16 bit time.

Receiver

The receiver of the 28L202 is conditioned to receive data when enabled through the command register. The receiver looks for a High-to-Low (mark-to-space) transition of the start bit on the RxD input pin. If a transition is detected, the state of the RxD pin is sampled each 16X clock for 7-1/2 clocks (16X clock mode) or at the next rising edge of the bit time clock (1X clock mode). If RxD is sampled high, the start bit is invalid and the search for a valid start bit begins again. If RxD is still low, a valid start bit is assumed. The receiver then continues to sample the input at one-bit time intervals at the theoretical center of the bit. When the proper number of data

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Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

bits and parity bit (if used) have been assembled, and one half-stop bit has been detected the receiver loads the byte to the FIFO. The least significant bit is received first. The data is then transferred to the Receive FIFO and the RxRDY bit in the SR is set to a 1. This condition can be programmed to generate an interrupt at OP4 or OP5 and INTRN. If the character length is less than 8 bits, the most significant unused bits in the RxFIFO are set to zero.

After the stop bit is detected, the receiver will immediately look for the next start bit. However, if a non-zero character was received with the stop bit at a zero level (framing error) and RxD remains Low for at least another one half bit time after the stop bit was sampled, then the receiver operates as if a new start bit had been detected. It then continues assembling the next character.

The error conditions of parity error, framing error, and overrun error (if any) are strobed into the SR at the received character boundary. This is just before the RxRDY status bit is set. If a break condition is detected (RxD is Low for the entire character including the stop bit), a character consisting of all zeros will be loaded into the RxFIFO and the received break bit in the SR is set to 1. The RxD input must return to high for two (2) clock edges of the X1 crystal clock for the receiver to recognize the end of the break condition and begin the search for a start bit.

This will usually require a high time of one X1 clock period or 3 X1 edges since the clock of the controller is not synchronous to the X1 clock.

Receiver Status Bits

There are five (5) status bits that are evaluated with each byte (or character) received: received break, framing error, parity error, overrun error, and change of break. The first three are appended to each byte and stored in the RxFIFO. The last two are not necessarily related to the byte being received or a byte that is in the RxFIFO. They are however developed by the receiver state machine.

The “received break” will always be associated with a zero byte in the RxFIFO. It means that zero character was a break character and not a zero data byte. The reception of a break condition will always set the “change of break” (see below) status bit in the Interrupt Status Register (ISR).

A framing error occurs when a non-zero character was seen and that character has a zero in the stop bit position.

The parity error indicates that the receiver-generated parity was not the same as that sent by the transmitter.

The overrun error occurs when the RxFIFO is full, the receiver shift register is full and another start bit is detected. At this moment the receiver has 257 valid characters and the start bit of the 258th has been seen. At this point the host has approximately 7/16 bit time to read a byte from the RxFIFO or the overrun condition will be set and the 258th character will overrun the 257th and the 258th the 259th and so on until an open position in the RxFIFO is seen. The fundamental meaning of the overrun is that data has been lost. Data in the RxFIFO remains valid. The receiver will begin placing characters in the RxFIFO as soon as a position becomes vacant.

Note: Precaution must be taken when reading an overrun FIFO. There will be 256th valid characters. Data will begin loading as soon as the first character is read. The 257th character will have been received as valid but it will not be known how many characters were lost between the two characters of the 256th and 257th reads of the RxFIFO

The “Change of break” means that either a break has been detected or that the break condition has been cleared. This bit is available in the ISR. The break change bit being set in the ISR and the received break bit being set in the SR will signal the beginning of a break. At the termination of the break condition only the change of break in the ISR will be set. After the break condition is detected the termination of the break will only be recognized when the RxD input has returned to the high state for two successive edges of the 1x clock; 1/2 to 1 bit time.

The receiver is disabled by reset or via CR commands. A disabled receiver will not interrupt the host CPU under any circumstance in the normal mode of operation. If the receiver is in the multi-drop or special mode, it will be partially enabled and thus may cause an interrupt. Refer to section on Wake-Up and the register description for MR1 for more information.

Receiver FIFO

The receiver buffer memory is a 256 byte FIFO with three status bits appended to each data byte. (The FIFO is then 256 11-bit “words”). The receiver state machine gathers the bits from the receiver shift register and the status bits from the receiver logic and writes the assembled byte and status bits to the RxFIFO. Logic associated with the FIFO encodes the number of filled positions for presentation to the interrupt arbitration system. The encoding is always 1 less than the number of filled positions. Thus, a full RxFIFO will bid with the value or 255; when empty it will not bit at all; one position occupied bids with the value 0. An empty FIFO will not bid since no character is available. Normally RxFIFO will present a bid to the arbitration system whenever it has one or more filled positions. The MR2 [3:2 bits allow the user to modify this characteristic so that bidding will not start until one of four levels (one or more filled, 1/2 filled, 3/4 filled, full) have been reached. As will be shown later this feature may be used to make slight improvements in the interrupt service efficiency. A similar system exists in the transmitter.

RxFIFO Status Bits. Status reporting modes

The description below applies to the upper three bits in the “Status Register” These three bits are not “in the status register”; they are part of the RxFIFO. The three status bits at the top of the RxFIFO are presented as the upper three bits of the status register included in each UART.

The error status of a character, as reported by a read of the SR (status register upper three bits) can be provided in two ways, as programmed by the error mode control bit in the mode register: “Character mode ” or the “Block Mode”. The block mode may be further modified (via a CR command) to set the status bits as the characters enter the FIFO or as they are read from the FIFO.

In the ’character’ mode, status is provided on a character by character basis as the characters are read from the RxFIFO: the “status” applies only to the character at the top of the RxFIFO – The next character to be read.

In the ’block’ mode, the status provided in the SR for these three bits is the logical OR of the status for all characters coming to the top of the RxFIFO, since the last reset error command was issued. In this mode each of the status bits stored in the RxFIFO are passed through a latch as they are sequentially written to the receiver FIFO. If any of the characters has an error bit set that latch will set and remain set until it is reset with a “receiver reset” is issued from the command register or a chip reset is issued. The purpose of this mode is indicating an error in the data block as opposed to an error in a character.

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1998 Oct 05

The latch used in the block mode to indicate “problem data” is usually set as the characters are read out of the RxFIFO. Via a command in the CR the latch may be configured to set the latch as the characters are pushed (loaded to) the RxFIFO. This gives the advantage of indicating “problem data” up to 256 (or the FIFO size) characters earlier.

In either mode, reading the SR does not affect the RxFIFO. The RxFIFO is ’popped’ only when the RxFIFO is read. Therefore, the SR should be read prior to reading the corresponding data character.

If the RxFIFO is full when a new character is received, the character is held in the receiver shift register until a position is available in the RxFIFO. At this time there are 257 valid characters in the RxFIFO. If an additional character is received while this state exists, the contents of the RxFIFO are not affected: the character previously in the shift register is lost and the overrun error status bit, SR [4], will be set upon receipt of the start bit of the new (overrunning) character.

Wake Up Mode

The SC28L202 provides two modes of this common asynchronous “party line” protocol: the new automatic mode with 3 sub modes and the default Host operated mode. The automatic mode has several sub modes (see below). In the full automatic the internal state machine devoted to this function will handle all operations associated with address recognition, data handling, receiver enables and disables. In both modes the meaning of the parity bit is changed. It is often referred to as the A/D bit or the address/data bit. It is used to indicate whether the byte presently in the receiver shift register is an “address” byte or a “data” byte. “1” usually means address; “0” data.

Its purpose is to allow several receivers connected to the same data source to be individually addressed. Of course addressing could be by group also. Normally the “Master” would send an address byte to all receivers “listening”. The receiver will then recognize its address and then enable itself to receive the following data stream. Upon receipt of an address not its own it would then disable itself. As descried below appropriate status bits are available to describe the operation.

Enabling the Wake Up mode

This mode is selected by programming bits MR1 [4:3] to ’11’. The sub modes are controlled by bits 6, 1, 0 in the MR0 register. Bit 6 controls the loading of the address byte to the RxFIFO and MR0 [1:0] determines the sub mode as shown in the following list.

•MR0 [1:0] = 00 Normal Wake Up Mode (default). Host controls

operation via interrupts and commands written to the command register (CR).

•MR0 [1:0] = 01 Auto wake. Enable receiver on address

recognition for this station. Upon recognition of its assigned address the local receiver will be enabled and normal receiver communications with the host will be established.

•MR0 [1:0] = 10 Auto Doze. Disable receiver on address

recognition, not for this station. Upon recognition of an address character that is not its own, in the Auto Doze mode, the receiver will be disabled and the address just received either discarded or pushed to the RxFIFO depending on the programming of MR0 [6].

•MR0 [1:0] = 11 Auto wake and doze. Both modes described

above. The programming of MR0 [1:0] to 11 will enable both the auto wake and auto doze features.

The enabling of the wake-up mode executes a partial enabling of the receiver state machine. Even though the receiver has been reset the wake up mode will over ride the disable and reset condition.

Normal Wake up (The default configuration)

In the default (mode “00” above and the least efficient) configuration for this mode of operation, a ’master’ station transmits an address character followed by data characters for the addressed ’slave’ station. The slave stations, whose receivers are normally disabled (not reset), examine the received data stream. Upon recognition of its address bit interrupts the CPU (by setting RxRDY). The CPU (host) compares the received address to its station address and enables the receiver if it wishes to receive the subsequent data characters. Upon receipt of another address character, the CPU may disable the receiver to initiate the process again.

A transmitted character consists of a start bit, the programmed number of data bits, an address/data (A/D) bit, and the programmed number of stop bits. The CPU selects the polarity of the transmitted A/D bit by programming bit MR1 [2]. MR1 [2] = 0 transmits a zero in the A/D bit position which identifies the corresponding data bits as data. MR1 [2] = 1 transmits a one in the A/D bit position which identifies the corresponding data bits as an address. The CPU should program the mode register prior to loading the corresponding data bytes into the TxFIFO.

While in this mode, the receiver continuously looks at the received data stream, whether it is enabled or disabled. If disabled, it sets the RxRDY status bit and loads the character into the RxFIFO if the received A/D bit is a one, but discards the received character if the received A/D bit is a zero. If the receiver is enabled, all received characters are transferred to the CPU via the RxFIFO. In either case, the data bits are loaded into the data FIFO while the A/D bit is loaded into the status FIFO position normally used for parity error (SR [5]). Framing error, overrun error, and break detect operate normally whether or not the receiver is enabled.

Receiver Reset and Disable

Receiver disable stops the receiver immediately – data being assembled in the receiver shift register is lost. Data and status in the FIFO is preserved and may be read. A re-enable of the receiver after a disable will cause the receiver to begin assembling characters at the next start bit detected. A receiver reset will discard the present shift register date, reset the receiver ready bit (RxRDY), clear the status of the byte at the top of the FIFO and re-align the FIFO read/write pointers. This effectively “clears” the receiver FIFO although the FIFO data is not altered.

A ‘watchdog timer’ is associated with each receiver. Its interrupt is enabled by MR0 [7]. The purpose of this timer is to alert the control processor that characters are in the RxFIFO which have not been read and/or the data stream has stopped. This situation may occur at the end of a transmission when the last few characters received are not sufficient to cause an interrupt. This counter times out after 64 bit times. It is reset each time a character is transferred from the receiver shift register to the RxFIFO or a read of the RxFIFO is executed.

Receiver Time-out Mode

In addition to the watch dog timer described in the receiver section, the counter/timer may be used for a similar function. Its programmability, of course, allows much greater precision of timeout intervals.

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Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

The time-out mode uses the received data stream to control the counter. Each time a received character is transferred from the shift register to the RxFIFO, the counter is restarted. If a new character is not received before the counter reaches zero count, the counter ready bit is set, and an interrupt can be generated. This mode can be used to indicate when data has been left in the RxFIFO for more than the programmed time limit. Otherwise, if the receiver has been programmed to interrupt the CPU when the receive FIFO is full, and the message ends before the FIFO is full, the CPU may not know there is data left in the FIFO. The CTU and CTL value would be programmed for just over one character time, so that the CPU would be interrupted as soon as it has stopped receiving continuous data. This mode can also be used to indicate when the serial line has been marking for longer than the programmed time limit. In this case, the CPU has read all of the characters from the FIFO, but the last character received has started the count. If there is no new data during the programmed time interval, the counter ready bit will get set, and an interrupt can be generated.

Writing the appropriate command to the command register enables the time-out mode. Writing an ‘Ax’ to CRA or CRB will invoke the time-out mode for that channel. Writing a ‘Cx’ to CRA or CRB will disable the time-out mode. The time-out mode should only be used by one channel at once, since it uses the C/T. If, however, the time-out mode is enabled from both receivers, the time-out will occur only when both receivers have stopped receiving data for the time-out period. CTU and CTL must be loaded with a value greater than the normal receive character period. The time-out mode disables the regular STAR T/STOP Counter commands and puts the ca/T into counter mode under the control of the received data stream. Each time a received character is transferred from the shift register to the RxFIFO, the C/T is stopped after 1 C/T clock, reloaded with the value in CTU and CTL and then restarted on the next C/T clock. If the C/T is allowed to end the count before a new character has been received, the counter ready bit, ISR [3], will be set. If IMR [3] is set, this will generate an interrupt. Receiving a character after the C/T has timed out will clear the counter ready bit, ISR [3], and the interrupt. Invoking the ‘Set Time-out Mode On’ command, CRx = ‘Ax’, will also clear the counter ready bit and stop the counter until the next character is received.

Time Out Mode Caution

When operating in the special time out mode, it is possible to generate what appears to be a “false interrupt”, i.e. an interrupt without a cause. This may result when a time-out interrupt occurs and then, BEFORE the interrupt is serviced, another character is received, i.e. the data stream has started again. (The interrupt latency is longer than the pause in the data stream.) In this case, when a new character has been receiver, the receiver, thereby withdrawing its interrupt will restart the counter/timer. If, at this time, the interrupt service begins for the previously seen interrupt, a read of the ISR will show the “Counter Ready” bit not set. If nothing else is interrupting, this read of the ISR will return a x’00 character.

CRC Modes and Control

The CRC (Cyclic Redundancy Check) control. The CRC generator may be programmed to one of four modes as

listed below.

•CRC16: Divisor – x 16 + x 15 + x 2 + 1, dividend preset to zeros.

– The Tx sends the calculated CRC non-inverted. – The Rx indicates an error if the computed CRC is not equal to 0.

•CRC16: Divisor = x 16 + x 15 + x 2 + 1, dividend preset to ones.

– The Tx sends the calculated CRC non-inverted. The

– Rx indicates an error if the computed CRC is not equal to 0.

•CRC–CCITT: Divisor = x 16 + x 12 + x 5 + 1, dividend preset to zeros

– The Tx sends the calculated CRC non-inverted. – The Rx indicates an error if the computed CRC is not equal to 0.

•CRC–CCITT: Divisor = x 16 + x 12 + x 5 + 1, dividend preset to ones

– The Tx sends the calculated CRC inverted. The

Rx indicates an error if the computed CRC is not equal to 0xF0B8’. Data sent to the CRC generator will exclude the stop, parity and

stop bits. The CRC remainder may be read from the CRC registers if desired.

Interrupt Arbitration

Interrupt Control

The interrupt system determines when an interrupt should be asserted thorough an arbitration (or bidding) system. This arbitration is exercised over the several systems within the DUART that may generate an interrupt. These will be referred to as “interrupt sources”. There are 18 in all. In general the arbitration is based on the fill level of the receiver FIFO or the empty level of the transmitter FIFO. The FIFO levels are encoded into an 8-bit number, which is concatenated to the channel number and source identification code. All of this is compared (via the bidding or arbitration process) to a user defined “threshold”. Whenever a source exceeds the numerical value of the threshold the interrupt will be generated.

At the time of interrupt acknowledge (IACKN) the source which has the highest bid (not necessarily the source that caused the interrupt to be generated) will be captured in a “Current Interrupt Register” (CIR). This register will contain the complete definition of the interrupting source: channel, type of interrupt (receiver, transmitter, change of state, etc.), and FIFO fill level. The value of the bits in the CIR are used to drive the interrupt vector and global registers such that controlling processor may be steered directly to the proper service routine. A single read operation to the CIR provides all the information needed to qualify and quantify the most common interrupt sources.

The interrupt sources for each channel are listed below.

•Transmit FIFO empty level for each channel

•Receive FIFO Fill level for each channel

•Change in break received status for each channel

•Receiver with error for each channel

•Change of state on channel input pins

•Receiver Watch-dog Time out Event

•Xon/Xoff character recognition

•Address character recognition

•Counter/Timer

Associated with the interrupt system are the interrupt mask register (IMR) and the interrupt status register (ISR) resident in each UART. Programming of the IMR selects which of the above sources may enter the arbitration process. Only the bidders in the ISR whose associated bit in the IMR is set to one (1) will be permitted to enter the arbitration process. The ISR can be read by the host CPU to determine all currently active interrupting conditions. For

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Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

convenience the bits of the ISR may be masked by the bits of the IMR. The setting of bit 6 in MR1 controls whether the ISR is read unmasked or masked.

Enabling and Activating Interrupt sources

An interrupt source becomes enabled when writing a one to the proper Interrupt Mask Register bit (IMR) activates its interrupt capability . An interrupt source can never generate an IRQN or have its “bid” or interrupt number appear in the CIR unless the source has been enabled by the appropriate bit in an IMR.

An interrupt source is active if it is presenting its bid to the interrupt arbiter for evaluation. Most sources have simple activation requirements. The watch-dog timer, break received, Xon/Xoff or Address Recognition and change of state interrupts become active when the associated events occur and the arbitration value generated thereby exceeds the threshold value programmed in the ICR (Interrupt Control Register).

The transmitter and receiver functions have additional controls to modify the condition upon which the initiation of interrupt “bidding” begins: the TxINT and RxINT fields of the MR0 and MR2 registers. These fields can be used to start bidding or arbitration when the RxFIFO is not empty, 50% full, 75% full or 100% full. For the transmitter it is not full, 50% empty, 75% empty and empty.

Example: To increase the probability of transferring the contents of a nearly full RxFIFO, do not allow it to start bidding until 50% or 75%

full. This will prevent its relatively high priority from winning the arbitration process at low fill levels. A high threshold level could accomplish the same thing, but may also mask out low priority interrupt sources that must be serviced. Note that for fast channels and/or long interrupt latency times using this feature should be used with caution since it reduces the time the host CPU has to respond to the interrupt request before receiver overrun occurs.

Setting interrupt priorities

The bid or interrupt number presented to the interrupt arbiter is composed of character counts, channel codes, fixed and programmable bit fields. The interrupt values are generated for various interrupt sources as shown in the table below: The value represented by the bits 11 to 4 in the table below are compared against the value represented by the “Threshold. The “Threshold”, bits 6 to 0 of the ICR (Interrupt Control Register), is aligned such that bit 6 of the threshold is compared to bit 9 of the interrupt value generated by any of the sources. Whenever the value of the interrupt source is greater than the threshold the interrupt will be generated.

The channel number arbitrates only against other channels. The threshold is not used for the channel arbitration. This results in channel B having the highest arbitration number. The decreasing order is B to A. If all other parts of an arbitration cycle are equal then the channel number will determine which channel will dominate in the arbitration process.

TYPE

B11–B7

БББББББ

BITS 2:0

Receiver w/o error

RxFIFO Byte Count –1

БББББББ

Channel No

Receiver w/ error

RxFIFO Byte Count –1

БББББББ

Channel No

Transmitter

TxFIFO Byte Count –1

БББББББ

Channel No

Change of Break

Programmed Field

БББББББ

Channel No

Change of State

Programmed Field

БББББББ

Channel No

Xon/Xoff

Programmed Field

БББББББ

Channel No

Address Recognition

Programmed Field

БББББББ

Channel No

Receiver Watch-dog

RxFIFO Byte Count –1

As RxFIFO Above

БББББББ

Channel No

Threshold

Bits 6:0 of Interrupt Control Register

БББББББ

000

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1998 Oct 05

Note several characteristics of the above table in bits 6:3. These bits contain the identification of the bidding source as indicated below:

0000 No interrupt source active 0x001 Receiver without error x101 Receiver with error (errors are: parity, framing and

overrun. Break is not considered an error) xx00 Transmitter 0010 Change of Break 0110 Change of State on I/O Ports 0111 Xon/Xoff Event 00111 Address Recognition 0011 Counter/Timer

The codes form bits 4:0 drive part of the interrupt vector modification and the Global Interrupt Type Register. The codes are unique to each source type and identify them completely. The channel numbering progresses from “A” to “B” as the binary numbers 0 to 1 and identify the interrupting channel uniquely. As the channels arbitrate “B” will have the highest bidding value and “A” the lowest

Note that the transmitter byte count is offset from that of the receiver by one bit. This is to give the receiver more authority in the arbitration since and over-run receiver corrupts the message but an under-run transmitter is not harmful. This puts some constraints on how the threshold value is selected. If a threshold is chosen that has its MSB set to one then a transmitter can never generate an interrupt! Of course the counter point to this is the desire to set the interrupt threshold high so interrupts occur only when a maximum or near maximum number of characters may be transferred.

To give some control over this dilemma control bits have been provided in the MR0 and MR2 registers of each channel to individually control when a receiver or transmitter may interrupt. The use of these bits will prevent a receiver or a transmitter from entering the arbitration process even though its FIFO fill level is above that indicated by the threshold value set. The bits in the MR0 and MR2 register are named TxINT (MR0 [5:4]) and RxINT (MR2 [3:2])

Interrupt Arbitration and IRQN generation

Interrupt arbitration is the process used to determine that an interrupt request should be presented to the host. The arbitration is carried out between the “Interrupt Threshold” and the “sources” whose interrupt bidding is enabled by the IMR. The interrupt threshold is part of the ICR (Interrupt Control Register) and is a value programmed by the user. The “sources” present a value to the interrupt arbiter. That value is derived from four fields: the channel number, type of interrupt source, FIFO fill level, and a programmable value. Only when one or more of these values exceeds the threshold value in the interrupt control register will the interrupt request (IRQN) be asserted.

Following assertion of the IRQN the host will either assert IACKN (Interrupt Acknowledge) or will use the command to “Update the CIR”. At the time either action is taken the CIR will capture the value of the source that is prevailing in the arbitration process. (Call this value the winning bid).

The X1clk drives the arbitration process. It scans the 12 bits of the arbitration bus at the X1clk rate developing a value for the CIR every 26 X1 cycles. New arbitration values presented to the arbitration

block during an arbitration cycle will be evaluated in the next arbitration cycle.

For sources other than receiver and transmitters the user may set the high order bits of an interrupt source’s bid value, thus tailoring the relative priority of the interrupt sources. The fill level of their respective FIFOs controls the priority of the receivers and transmitters. The more filled spaces in the RxFIFO the higher the bid value; the more empty spaces in the TxFIFO the higher its priority. Channels whose programmable high order bits are set will be given interrupt priority higher than those with zeros in their high order bits, thus allowing increased flexibility. The transmitter and receiver bid values contain the character counts of the associated FIFOs as high order bits in the bid value. Thus, as a receiver’s RxFIFO fills, it bids with a progressively higher priority for interrupt service. Similarly, as empty space in a transmitter’s TxFIFO increases, its interrupt arbitration priority increases.

IACKN Cycle, Update CIR

When the host CPU responds to the interrupt, it will usually assert the IACKN signal low. This will cause the DUART to generate an IACKN cycle in which the condition of the interrupting device is determined. When IACKN asserts, the last valid interrupt number is captured in the CIR. The value captured presents most of the important details of the highest priority interrupt at the moment the IACKN (or the “Update CIR” command) was asserted.

The Dual UART will respond to the IACKN cycle with an interrupt vector. The interrupt vector may be a fixed value, the content of the Interrupt Vector Register, or when “Interrupt Vector Modification” is enabled via ICR, it may contain codes for the interrupt type and/or interrupting channel. This allows the interrupt vector to steer the interrupt service directly to the proper service routine. The interrupt value captured in the CIR remains until another IACKN cycle occurs or until an “Update CIR” command is given to the DUART. The interrupting channel and interrupt type fields of the CIR set the current “interrupt context” of the DUART. The channel component of the interrupt context allows the use of Global Interrupt Information registers that appear at fixed positions in the register address map. For example, a read of the Global RxFIFO will read the channel B RxFIFO if the CIR interrupt context is channel b receiver. At another time read of the GRxFIFO may read the channel D RxFIFO (CIR holds a channel D receiver interrupt) and so on. Global registers exist to facilitate qualifying the interrupt parameters and for writing to and reading from FIFOs without explicitly addressing them.

The CIR will load with x’00 if IACKN or Update CIR is asserted when the arbitration circuit is NOT asserting an interrupt. In this condition there is no arbitration value that exceeds the threshold value. When Interrupt vector modification is active in this situation the interrupt vector bits associated with the CIR will all be zero.

Global Registers

The “Global Registers”, 19 in all, are driven by the interrupt system. These are not real hardware devices. They are defined by the content of the CIR (Current Interrupt Register) as a result of an interrupt arbitration. In other words they are indirect registers pointed to by the content of the CIR. The list of global register follows:

•GIBCR The byte count of the interrupting FIFO

•GICR Channel number of the interrupting channel

•GITR Type identification of interrupting channel

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1998 Oct 05

•GRxFIFO Pointer to the interrupting receiver FIFO

•GTxFIFO Pointer to the interrupting transmitter FIFO

A read of the GRxFIFO will give the content of the RxFIFO that presently has the highest bid value. The purpose of this system is to enhance the efficiency of the interrupt system. The global registers and the CIR update procedure are further described in the Interrupt Arbitration system

Polling

Many users prefer polled to interrupt driven service where there are not a large number of fast data channels and/or the host CPU’s other interrupt overhead is low. The Dual UART is functional in this environment.

The most efficient method of polling is the use of the “update CIR” command (with the interrupt threshold set to zero) followed by a read of the CIR. This dummy write cycle will perform the same CIR capture function that an IACKN falling edge would accomplish in an interrupt driven system. A subsequent read of the CIR, at the same address, will give information about an interrupt, if any. If the CIR contains 0s, no interrupt is awaiting service. If the value is non-zero, the fields of the CIR may be decoded for type; channel and character count information. Optionally, the global interrupt registers may be read for particular information about the interrupt status or use of the global RxD and TxD registers for data transfer as appropriate. The interrupt context will remain in the CIR until another update CIR command or an IACKN cycle is initiated by the host CPU occurs. The CIR loads with x’00 if Update CIR is asserted when the arbitration circuit has NOT detected an arbitration value that exceeds the threshold value of the ICR. The global registers and CIR may be used as “vectors” to the service type required.

Traditional methods of polling status registers may also be used. They of course are less efficient but give the most variable and quickest method of changing the order in which interrupt sources are evaluated and interrogated.

Character Recognition

Character recognition is specific to each of the two UARTs. Three programmable characters are provided for the character recognition for each channel. The three are general purpose in nature and may be set to only cause an interrupt or to initiate some rather complex operations specific to “Multi-drop” address recognition or in-band Xon/Xoff flow control.

Character recognition is accomplished via CAM memory. The Content Addressable Memory continually examines the incoming data stream. Upon the recognition of a control character appropriate bits are set in the Xon/Xoff Interrupt Status Register (XISR) and Interrupt Status Register (ISR). The setting of these bit(s) will initiate any of the automatic sequences or and/or an interrupt that may have enabled via the MR0 register.

The characters of the recognition system are fully programmable. The Xon/Xoff characters may be set to the standard characters if the hardware preconditioning is set by the PRE pin. They do not have a pre-defined “reset value” They may, however, be loaded by a “Gang Write” or “Gang Load” command as described in the “Xon Xoff Characters” paragraph.

The character recognition circuits are basically designed to provide general-purpose character recognition. Additional control logic has been added to allow for Xon/Xoff flow control and for recognition of

the address character in the multi-drop or “wake-up” mode. This logic also allows for the generation of interrupts in either the general-purpose recognition mode or the specific conditions mentioned above.

Xon Xoff Characters

The programming of these characters is usually done individually. However a method has been provided to write to all of registers in one operation by way of the “Gang Load” and “Gang Write” commands provided in the channel A Command Register. When these commands are executed all registers are programmed with the same characters. The “write” command loads a used defined character; the “load” command loads the standard Xon/Xoff characters. Xon is 0x11, Xof f 0x13. Any enabling of the Xon/Xoff functions will use the contents of the Xon and Xoff character registers as the basis on which recognition is predicated.

Multi-drop or Wake up or 9 bit mode

This mode is used to address a particular UART among a group connected to the same serial data source. Normally it is accomplished by redefining the meaning of the parity bit such that it indicates a character as address or data. While this method is fully supported in the SC28L202 it also supports recognition of the character itself. Upon recognition of its address the receiver will be enabled and data pushed onto the RxFIFO.

Further the Address recognition has the ability, if so programmed, to disable (not reset) the receiver when an address is seen that is not recognized as its own. The particular features of “Auto Wake and Auto Doze” are described in the detail descriptions below.

Note: Care should be taken in the programming of the character recognition registers. Programming x’00, for example, may result in a break condition being recognized as a control character. This will be further complicated when binary data is being processed.

Character Stripping

The MR0 register provides for stripping the characters used for character recognition. Recall that the character recognition may be conditioned to control several aspects of the communication. However this system is first a character recognition system. The status of the various states of this system is reported in the XISR and ISR registers. The character stripping of this system allows for the removal of the specified control characters from the data stream: two for the Xon /Xoff and one for the wake up. Via control in the MR0 register these characters may be discarded (stripped) from the data stream when the recognition system “sees” them or they may be sent on the RxFIFO. Whether they are stripped or not the recognition system will process them according to the action requested; flow control, wake up, interrupt generation, etc. Care should be exercised in programming the stripping option if noisy environments are encountered. If a normal character were corrupted to an Xoff character the transmitter would be stopped. If that character were now stripped from the FIFO stack, then that stripping action would make it difficult to determine the cause of transmitter stopping.

Receiver Mode

Since the receiving FIFO resources in the Dual UART are limited, some means of controlling a remote transmitter is desirable in order to lessen the probability of receiver overrun. The Dual UART provides two methods of controlling the data flow. There is a hardware-assisted means of accomplishing control, the so-called out-of-band flow control, and an in-band flow control method.

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1998 Oct 05

The out-of-band flow control is implemented through the CTSN–RTSN signaling via the I/O ports. The operation of these hardware handshake signals is described in the receiver and transmitter discussions.

In-band flow control is a protocol for controlling a remote transmitter by embedding special characters within the message stream, itself. Two characters, Xon and Xoff, which do not represent normal printable character take on flow control definitions when the Xon/Xoff capability is enabled. Flow control characters received may be used to gate the channel transmitter on and off. This activity is referred to as Auto-transmitter mode. To protect the channel receiver from overrun, fixed fill levels (hardware set at 12 characters) of the RxFIFO may be employed to automatically insert Xon/Xoff characters in the transmitter’s data stream. This mode of operation is referred to as auto-receiver mode. Commands issued by the host CPU via the CR can simulate all these conditions.

Auto-transmitter mode

When a channel receiver pushes an Xoff character into the RxFIFO, the channel transmitter will finish transmission of the current character and then stop transmitting. A transmitter so idled can be restarted by the receipt of an Xon character by the receiver or by a hardware or software reset. The last option results in the loss of the un-transmitted contents of the TxFIFO. When operating in this mode the Command Register commands for the transmitter are not effective.

While idle data may be written to the TxFIFO and it continue to present its fill level to the interrupt arbiter and maintains the integrity of its status registers.

Use of ’00’ as an Xon/Xoff character is complicated by the Receiver break operation which pushes a ’00’ character on the RxFIFO. The Xon/Xoff character detectors do not discriminate this case from an Xon/Xoff character received through the RxD pin.

Note: To be recognized as an Xon or Xoff character, the receiver must have room in the RxFIFO to accommodate the character. An Xon/Xoff character that is received resulting in a receiver overrun does not effect the transmitter nor is it pushed into the RxFIFO, regardless of the state of the Xon/Xoff transparency bit, MR0 (7).

Xon /Xoff characters

The Xon/Xoff character with errors will be accepted as valid. The user has the option sending or not sending these characters to the FIFO. Error bits associated with Xon/Xoff will be stored normally to the receiver FIFO.

The channel’s transmitter may be programmed to automatically transmit an Xoff character without host CPU intervention when the RxFIFO fill level exceeds a fixed limit (12). In this mode it will transmit an Xon character when the RxFIFO level drops below a second fixed limit (8). A character from the TxFIFO that has been loaded into the TxD shift register will continue to transmit. Character(s) in the TxFIFO that have not been loaded to the transmitter shift register are unaffected by the Xon or Xoff transmission. They will be transmitted after the Xon/Xoff activity concludes.

If the fill level condition that initiates Xon activity negates before the flow control character can begin transmission, the transmission of the flow control character will not occur, i.e. either of the following sequences may be transmitted depending on the timing of the FIFO level changes with respect to the normal character times:

Character Xoff Xon Character Character Character

Hardware keeps track of Xoff characters sent that are not rescinded by an Xon. This logic is reset by writing MR0 (3) to ’0’. If the user drops out of Auto-receiver mode while the XISR shows Xoff as the last character sent the Xon/Xoff logic would not automatically send the negating Xon.

Host mode

When neither the auto-receiver or auto-transmitter modes are set, the Xon/Xoff logic is operating in the host mode. In host mode, all activity of the Xon/Xoff logic is initiated by commands to the CRx. The Xoff command forces the transmitter to disable exactly as though an Xoff character had been received by the RxFIFO. The transmitter will remain disabled until the chip is reset or the CR (7:3) = 10110 (Xof f resume) command is given. In particular, reception of an Xon or disabling or re-enabling the transmitter will NOT cause resumption of transmission. Redundant CRTX—commands, i.e. CRTXon CRTXon, are harmless, although they waste time. A CRTXon may be used to cancel a CRTXoff (and vice versa) but both may be transmitted depending on the command timing with respect to that of the transmitter state machine.

The kill CRTX command can be used to cleanly terminate any CRTX commands pending with the minimum impact on the transmitter.

Note: In no case will an Xon/Xoff character transmission be aborted.

Once the character is loaded into the TX Shift Register, transmission continues until completion or a chip reset is encountered.

The kill CRTX command has no effect in either of the Auto modes.

Mode control

Xon/Xoff mode control is accomplished via the MR0. Bits 3 and 2 reset to zero resulting in all Xon/Xoff processing being disabled. If MR0 [2] is set, Xon/Xoff characters received may gate the transmitter. If MR0 [3] is set, the transmitter will transmit Xon and Xoff when triggered by attainment of fixed fill levels in the channel RxFIFO. The MR0 [7] bit also has an Xon/Xoff function control. If this bit is set, a received Xon or Xoff character is not pushed into the RxFIFO. If cleared, the power-on and reset default, the received Xon or Xoff character is pushed onto the RxFIFO for examination by the host CPU. The MR0 (7) function operates regardless of the value in MR0 (3:2).

Xon/Xoff Interrupts

The Xon/Xoff logic generates interrupts only in response to recognizing either of the characters in the XonCR or XoffCR (Xon or Xoff Character Registers). The transmitter activity initiated by the Xon/Xoff logic or any CR command does not generate an interrupt. The character comparators operate regardless of the value in MR0 (3:2). Hence the comparators may be used as general-purpose character detectors by setting MR0 (3:2)=’00’ and enabling the Xon/Xoff interrupt in the IMR.

The Dual UART can present the Xon/Xoff recognition event

to the interrupt arbiter for IRQN generation. The IRQN generation may be masked by setting bit 4 of the Interrupt Mask Register, IMR. The bid level of an Xon/Xoff recognition event is controlled by the Bidding Control Register X, BCRX, of the channel. The interrupt status can be examined in ISR [4]. If cleared, no Xon/Xoff recognition event is

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1998 Oct 05

interrupting. If set, an Xon or Xoff recognition event has been detected. The X Interrupt Status Register, XISR, can be read for details of the interrupt and to examine other, non-interrupting, status of the Xon/Xoff logic. Refer to the XISR in the Register Descriptions.

The character recognition function and the associated interrupt generation is disabled on hardware or software reset.

FIFO Partitioning and Control

FIFO Control for Variable Partitions of RAM.

The FIFO for this DUART is based on static ram memory. A base block of 1024 11-bit bytes of memory is used. On reset this memory is partitioned into 256 bytes for each receiver and transmitter with an interrupt level set at 128 bytes or half full. However the size of each partition is under program control and may be varied from 0 to 1021 bytes

Fifo interrupt is also variable and may be set at any level within the partition. Xon and Xoff levels are set to 8 bytes below the full level of the partition size used.

Memory control uses 10 bit registers to control the “FIFO” partition size and interrupt level for each receiver and transmitter. These control registers use a basic 8 bit register and another 8-bit register that contains two bits for each partition that is set to a size above 255 bytes.

FIFO control registers.

Each FIFO has three principal registers: size, interrupt level and two bits in the FIFO page register. The FIFO size and the FIFO’s two bits in the page register comprise a total of ten (10) bits that will be used by the FIFO control engine to set up the address. The reset value of these registers will configure the FIFOs to a size of 256 (0xFF) bytes and an interrupt level of 128 (0x80). The bits of the page register are set a 0 (0x00).

The meaning of the FIFO interrupt level is defined to mean the remaining bytes that are available in the FIFO before it is filled. For example it the interrupt level is set a 50 and the fifo size is set at 220 then the interrupt will occur then the receiver fills to 170 bytes. For the transmitter the interrupt would extinguish when the transmitter FIFO was load with 170 bytes. Recall that a full transmitter FIFO will not generate an interrupt and that an empty receiver FIFO will not generate an interrupt

The transmitter buffer memory is a one byte register driven by the transmitter FIFO. The FIFO control writes characters to this buffer. This buffer accepts data only when the transmitter is enabled. The transmitter state machine reads them out in the order they were received and presents them to the transmitter shift register for serialization. The transmitter adds the required start, parity and stop bits as required by the MR2 register programming. The start bit (always one bit time in length) is sent first followed by the least significant bit (LSB) to the most significant bit (MSB) of the character, the parity bit (if used) and the required stop bit(s).

Logic associated with the FIFO encodes the number of empty positions available in an eight-bit value. This value is concatenated

with the channel number and type interrupt type identifier and presented to the interrupt arbitration system. The encoding of the “positions empty” value is always 1 less than the number of available positions. Thus, an empty TxFIFO will bid with the value of the partition size; when full it will not bid at all. One position empty bids with the value 0. A full FIFO will not bid since a character written to it will be lost

Normally a TxFIFO will present a bid to the arbitration system whenever it has one or more empty positions. The MR0 [5:4] allow the user to modify this characteristic so that bidding will not start until one of four levels (empty, 3/4 empty, 1/2 empty, not full) have been reached. As will be shown later this feature may be used to make slight improvements in the interrupt service efficiency . A similar system exists in the receiver.

PROGRAMMING

Writing control words into the appropriate registers programs the operation of the DUART. Operational feedback is provided via status registers that can be read by the CPU. The addressing of the registers is described in Table NO TAG.

The contents of certain control registers are initialized to zero on RESET. Care should be exercised if the contents of a register are changed during operation, since certain changes may cause operational problems.

For example, changing the number of bits per character while the transmitter is active may cause the transmission of an incorrect character. In general, the contents of the MR, the CSR, and the OPCR should only be changed while the receiver(s) and transmitter(s) are not enabled, and certain changes to the ACR should only be made while the C/T is stopped.

Each channel has 3 mode registers (MR0, 1, 2) which control the basic configuration of the channel. Independent MR address pointers control access to these registers. These pointers are set to 0 or 1 by MR control commands in the command register “Miscellaneous Commands”. Each time the MR registers are accessed the MR pointer increments, stopping at MR2. It remains pointing to MR2 until set to 0 or 1 via the miscellaneous commands of the command register. The pointer is set to 1 on reset for compatibility with previous Philips Semiconductors UART software.

Mode, command, clock select, and status registers are duplicated for each channel to provide total independent operation and control. Refer to Table 1 for register bit descriptions. The reserved registers at addresses H‘02’ and 0x0A’ should never be read during normal operation since they are reserved for internal diagnostics.

The registers of the SC28L202 are loosely partitioned into two groups: those used in controlling data channels and those used in handling the actual data flow and status. Tables 1 and 2 show the general configuration of all the register addresses.

NOTE: Some registers contain control bits that configure the entire chip. These are denoted by a “D” symbol

Page 23

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Table 1. Summary Register Map, Control

ББББББ

ADDRESS (HEX)

C = CHANNEL

ББББББББББББББ

ÁÁÁÁ

ACRONYM

БББББ

READ/WRITE

0c 0000 (0x00)

Mode Register 0 MR0A

MR0

R/W

0c 0001 (0x01)

Mode Register 1 MR1A

MR1

R/W 0c 0010 (0x02) 0c 0011 (0x03)

Bid Control, Break Change

BCRBRK

R/W 0c 0100 (0x04)

Bid Control, Change of State

BCRCOS

R/W 0c 0101 (0x05)

Reset Output Port Register

ROPR

0c 0110 (0x06)

Bid Control, Xon/Xoff

BCRX

R/W 0c 0111 (0x07)

Bid Control, Address recognition

BCRA

R/W 0c 1000 (0x08)

Xon Character Register

XonCR

R/W 0c 1001 (0x09)

Xoff Character Register

XoffCR

R/W 0c 1010 (0x0A)

Address Recognition Character

ARCR

R/W 0c 1100 (0x0C)

Receiver Clock Select Register

RxCSR

R/W 00 1101 (0x0D)

DTest Register

Reserved, set to 0

0c 1110 (0x0E)

Transmitter Clock Select Register

TxCSR

R/W 10 1110 (0x2C)

Set Output Port Register

SOPR

01 111 1 (0x1F)

DFIFO Partition Page Count

FPPC

R/W 01 1011 (0x1B)

DInterrupt Control Register

ICR

R/W 01 1101 (0x1D)

DWatch-dog Timer Run Control

WDTRCR

R/W 01 111 1 (0x1F)

DInterrupt Vector Register

IVR

R/W

Page 24

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

T able 2. Summary Register Map, Data

ÁÁÁ

ADDRESS (HEX)

C = CHANNEL

ББББББББББ

ÁÁÁ

ACRONYM

БББББББББ

ÁÁÁ

ACRONYM

1c 0000 (0xc0)

Mode Register 2

MR2

Mode Register 2

MR2

1c 0001 (0xc1)

Status Register

Command Register

1c 0010 (0xc2)

Interrupt Status Register

ISR

Interrupt Mask Register

IMR

1c 0011 (0xc3)

Receiver FIFO

RxFIFO

Transmitter FIFO

TxFIFO

1c 0100 (0xc4)

Input Port Register

IPR

1c 0101 (0xc5)

X Character Status Register

XISR

1c 0110 (0xc6)

Counter/Timer Lower

C/TL

Counter Timer Lower Preset

C/TLP

1c 0111 (0xc7)

Counter/Timer Upper

C/TU

Counter Timer Upper Preset

C/TUP

1c 1000 (0xc8)

FIFO Partition Register Rx

FP_RX

1c 1001 (0xc9)

FIFO Partition Register Tx

FP_Tx

1c 1010 (0xcA)

FIFO Interrupt Level Rx

FIL_Rx

1c 1011 (0xcB)

FIFO Interrupt Level Tx

FIL_Tx

1c 1100 (0xcC)

I/O Port Configuration 3–0

IOPCR3–0

10 1011 (0x2D)

DGlobal Interrupt Channel Register

GICR

I/O Port Configuration 7–4

IOPCR7–4

10 1110 (0x2E)

DGlobal Interrupt Byte Count

GIBCR

10 111 1 (0x2F)

DGlobal Interrupt Type Register

GITR

11 1011 (0x3D)

DCurrent Interrupt Register

CIR

DUpdate Current Interrupt Register

UCIR

11 11 10 (0x3E)

DGlobal Rx FIFO GRxFIFO

GRxFIFO

DGlobal TxFIFO GTxFIFO

GTxFIFO

11 11 11 (0x3F)

Page 25

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

The three MR Registers are accessed via the MR Pointer and Commands 0x1n and 0xBn (where n = represents receiver and transmitter enable bits)

Table 3. Register Bit Formats

These are support functions for both Channels

Input Port Change Register

IPCR

Auxiliary Control Register

ACR

R/W

Interrupt Status Register

ISR

Interrupt Mask Register

IMR

R/W

Counter Timer Upper Value

CTU

Counter Timer Lower Value

CTL

Counter Timer Preset Upper

CTPU

R/W

Counter Timer Preset Lower

CTPL

R/W

Input Port Register

IPR

Output Configuration Register

OPCR

R/W

Set Output Port

Bits

R/W

Reset Output Port

Bits

R/W

The following named registers are the same for Channels A and B

Mode

MRnA

MRnB

R/W

Status

SRA

SRB

R only

Clock

Select

CSRA

CSRB

R/W

Command

CRA

CRB

R/W

Receiver

FIFO

RxFIFOA

RxFIFOB

R only

Transmitter

FIFO

TxFIFOA

TxFIFOB

R/W

Table 4. Bit Rate Generator Characteristics

(Crystal or Clock = 14.7456 MHz)

ÁÁÁÁ

NORMAL RATE

(BAUD)

ÁÁÁÁ

ACTUAL 16X

CLOCK (KHZ)

БББББ

ERROR (%)

0.8

1.2

110

1.759

–0.069

134.5

2.153

0.059

150

2.4

200

3.2

300

4.8

600

9.6

1050

16.756

–0.260

1200

19.2

1800

28.8

2000

32.056

0.175

2400

38.4

4800

76.8

7200

115.2

9600

153.6

19.2K

307.2

38.4K

614.4

NOTE:

Duty cycle of 16X clock is 50% 1%.

Page 26

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

MR0A MR0 Mode Register 0 MR0 is accessed by setting the MR pointer to 0 via command B of the command register.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

ÁÁÁ

MR0A MR0B

MR0B[3:0] are

reserved

ÁÁÁ

Rx WATCH

DOG

0 = Disable

1 = Enable

ÁÁÁ

RxINT BIT 2

See Tables in

MR0 description

ÁÁÁ

TxINT (1:0)

See table 7

ÁÁÁÁ

DON’T CARE

Set to 0

ÁÁÁ

BAUD RATE

EXTENDED II

0 = Normal

1 = Extend II

ÁÁÁ

TEST 2

Set to 0

ÁÁÁ

BAUD RATE

EXTENDED

0 = Normal

1 = Extend

MR0 [7]—This bit controls the receiver watchdog timer. 0 = disable, 1 = enable. When enabled, the watch dog timer will generate a receiver interrupt if the receiver FIFO has not been accessed within 64 bit times of the receiver 1X clock. This is used to alert the control processor that data is in the RxFIFO that has not been read. This situation may occur when the byte count of the last part of a message is not large enough to generate an interrupt.

MR0 [6]—Bit 2 of receiver FIFO interrupt level. This bit along with Bit 6 of MR1 sets the fill level of the 8 byte FIFO that generates the receiver interrupt.

MR0 [6] MR1 [6] Note that this control is split between MR0 and MR1. This is for backward compatibility to the SCC2692 and SCN2681.

Table 5. Receiver FIFO Interrupt Fill Level

(MR0 (3)=0

MR0[6] MR1[6]

INTERRUPT CONDITION

1 or more bytes in FIFO (Rx RDY)

3 or more bytes in FIFO

6 or more bytes in FIFO

8 bytes in FIFO (Rx FULL)

Table 6. Receiver FIFO Interrupt Fill Level

(MR0 (3) = 1

MR0[6] MR1[6]

INTERRUPT CONDITION

1 or more bytes in FIFO (Rx RDY)

6 or more bytes in FIFO

12 or more bytes in FIFO

16 bytes in FIFO (Rx FULL)

For the receiver these bits control the number of FIFO positions empty when the receiver will attempt to interrupt. After the reset the receiver FIFO is empty. The default setting of these bits cause the receiver to attempt to interrupt when it has one or more bytes in it.

MR0 [5:4]—Tx interrupt fill level.

Table 7. Transmitter FIFO Interrupt Fill Level

MR0 (3) = 0

MR0[5:4]

INTERRUPT CONDITION

8 bytes empty (Tx EMPTY)

4 or more bytes empty

6 or more bytes empty

1 or more bytes empty (Tx RDY)

Table 8. Transmitter FIFO Interrupt Fill Level

MR0 (3) = 1

MR0[5:4]

INTERRUPT CONDITION

16 bytes empty (Tx EMPTY)

8 or more bytes empty

12 or more bytes empty

1 or more bytes empty (Tx RDY)

For the transmitter these bits control the number of FIFO positions empty when the receiver will attempt to interrupt. After reset the transmit FIFO has 256 bytes empty. It will then attempt to interrupt as soon as the transmitter is enabled. The default setting of the MR0 bits (00) condition the transmitter to attempt to interrupt only when it is completely empty. As soon as one byte is loaded, it is no longer empty and hence will withdraw its interrupt request.

MR0 [3]—Selects the FIFO depth at 8 or 16 bytes. See tables 5 and 7. MR0 [2:0]—These bits are used to select one of the six baud rate

groups. See Table 9 for the group organization.

000 Normal mode 001 Extended mode I

100 Extended mode II Other combinations of MR2 [2:0] should not be used. Note: MR0 [3:0] are not used in channel B and should be set to 0.

Page 27

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

MR1A MR1 MODE REGISTER 1

ÁÁÁÁ

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

ÁÁÁ

MR1A MR1B

ÁÁÁÁ

ÁÁ

CONTROLS

RTS

ÁÁÁ

RxINT

BIT 1

ÁÁÁ

ERROR

MODE

ББББББ

PARITY MODE

ÁÁÁ

PARITY

TYPE

ББББББ

BITS PER CHARACTER

ÁÁÁ

ÁÁÁÁ

ÁÁ

0 = No

1 = Yes

ÁÁÁ

0 = RxRDY

1 = FFULL

ÁÁÁ

0 = Char

1 = Block

ББББББ

00 = With Parity

01 = Force Parity

10 = No Parity

11 = Multi-drop Mode

ÁÁÁ

0 = Even

1 = Odd

ББББББ

00 = 5 01 = 6 10 = 7 11 = 8

NOTE:

1. In block error mode, using the error-reset command (command 0x4n) will clear block error conditions or a receiver reset.

MR1A is accessed when the Channel A MR pointer points to MR1. The pointer is set to MR1 by RESET or by a ‘set pointer’ command applied via CR command 1. After reading or writing MR1A, the pointer will point to MR2A.

MR1A [7]—Channel A Receiver Request-to-Send Control (Flow Control)

This bit controls the deactivation of the RTSAN output (OP0) by the receiver. This output is normally asserted by setting OPR [0] and negated by resetting OPR [0].

MR1A [7] = 1 causes RTSAN to be negated (OP0 is driven to a ‘1’ [V

]) upon receipt of a valid start bit if the Channel A FIFO is full. This is the beginning of the reception of the ninth byte. If the FIFO is not read before the start of the tenth byte, an overrun condition will occur and the tenth byte will be lost. However, the bit in OPR [0] is not reset and RTSAN will be asserted again when an empty FIFO position is available. This feature can be used for flow control to prevent overrun in the receiver. Use of the receiver’s R TSN output signal to control the CTSN input of the transmitting stops the transmitter when the receiver FIFO is full.

MR1 [6]—Bit 1 of the receiver interrupt control. See description under MR0 [6].

MR1A [5]—Channel A Error Mode Select

This bit selects the operating mode of the three FIFOed status bits (FE, PE, and received break) for Channel A. In the ‘character’

mode, status is provided on a character-by-character basis; the status applies only to the character at the top of the FIFO. In the ‘block’ mode, the status provided in the SR for these bits is the accumulation (logical-OR) of the status for all characters coming to the top of the FIFO since the last ‘reset error’ command for Channel A was issued.

MR1A [4:3|—Channel A Parity Mode Select

If ‘with parity’ or ‘force parity’ is selected a parity bit is added to the transmitted character and the receiver performs a parity check on incoming data MR1A [4:3] = 11 selects Channel A to operate in the special multi-drop mode described in the Operation section.

MR1A [2]—Channel A Parity Type Select

This bit selects the parity type (odd or even) if the ‘with parity’ mode is programmed by MR1A [4:3], and the polarity of the forced parity bit if the ‘force parity’ mode is programmed. It has no effect if the ‘no parity’ mode is programmed. In the special multi-drop mode it selects the polarity of the A/D bit.

MR1A [1:0]—Channel A Bits Per Character Select

This field selects the number of data bits per character to be transmitted and received. The character length does not include the start, parity, and stop bits.

Page 28

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

MR2A—Channel A Mode Register 2

MR2A is accessed when the Channel A MR pointer points to MR2, which occurs after any access to MR1A. Accesses to MR2A do not change the pointer.

MR2 MODE REGISTER 2

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

MR2A MR2B

CHANNEL MODE

Tx CONTROLS

RTS

CTS ENABLE

STOP BIT LENGTH

NOTE: Add 0.5 to binary codes 0–7 for 5 bit character lengths.

БББББ

00 = Normal 01 = Auto-Echo 10 = Local loop 11 = Remote loop

ÁÁÁÁ

0 = No

1 = Yes

ÁÁÁ

0 = No

1 = Yes

БББББББББББББББ

0 = 0.563 4 = 0.813 8 = 1.563 C = 1.813 1 = 0.625 5 = 0.875 9 = 1.625 D = 1.875 2 = 0.688 6 = 0.938 A = 1.688 E = 1.938 3 = 0.750 7 = 1.000 B = 1.750 F = 2.000

NOTE:

1. Add 0.5 to values shown for 0–7 if channel is programmed for 5 bits/char.

MR2A [7:6]—Channel A Mode Select

Each channel of the DUART can operate in one of four modes. MR2A [7:6] = 00 is the normal mode, with the transmitter and receiver operating independently.

MR2A [7:6] = 01 places the channel in the automatic echo mode, which automatically retransmits the received data. The following conditions are true while in automatic echo mode:

1. Received data is reclocked and retransmitted on the TxDA

output.

2. The receiver clock is used for the transmitter.

3. The receiver must be enabled, but the transmitter need not be

enabled.

4. The Channel A TxRDY and TxEMT status bits are inactive.

5. The received parity is checked, but is not regenerated for

transmission; i.e. transmitted parity bit is as received.

6. Character framing is checked, but the stop bits are retransmitted

as received.

7. A received break is echoed as received until the next valid start

bit is detected.

8. CPU to receiver communication continues normally, but the CPU

to transmitter link is disabled.

Two diagnostic modes can also be configured. MR2A [7:6] = 10 selects local loop back mode. In this mode:

1. The transmitter output is internally connected to the receiver

input.

2. The transmitter clock is used for the receiver.

3. The TxDA output is held High.

4. The RxDA input is ignored.

5. The transmitter must be enabled, but the receiver need not be

enabled.

6. CPU to transmitter and receiver communications continues

normally .

The second diagnostic mode is the remote loop back mode, selected by MR2A [7:6] = 11. In this mode:

1. Received data is reclocked and retransmitted on the TxDA

output.

2. The receiver clock is used for the transmitter.

3. Received data is not sent to the local CPU, and the error status conditions are inactive.

4. The received parity is not checked and is not regenerated for transmission, i.e., transmitted parity is as received.

5. The receiver must be enabled.

6. Character framing is not checked, and the stop bits are retransmitted as received.

7. A received break is echoed as received until the next valid start bit is detected.

The user must exercise care when switching into and out of the various modes. The selected mode will be activated immediately upon mode selection, even if this occurs in the middle of a received or transmitted character. Likewise, if a mode is deselected the device will switch out of the mode immediately. An exception to this is switching out of auto echo or remote loop back modes. If the de-selection occurs just after the receiver has sampled the stop bit (indicated in auto echo by assertion of RxRDY), and the transmitter is enabled, the transmitter will remain in auto echo mode until the entire stop has been re-transmitted.

MR2A [5]—Channel A Transmitter Request-to-Send Control This bit controls the deactivation of the RTSAN output (OP0) by the transmitter. This output is normally asserted by setting OPR [0] and negated by resetting OPR [0]. MR2A [5] = 1 caused OPR [0] to be reset automatically one bit time after the characters in the Channel A transmit shift register and in the TxFIFO, if any, are completely transmitted including the programmed number of stop bits, if the transmitter is not enabled.

This feature can be used to automatically terminate the transmission of a message as follows:

1. Program auto-reset mode: MR2A [5] = 1.

2. Enable transmitter.

3. Asset RTSAN: OPR [0] = 1.

4. Send message.

5. Disable transmitter after the last character is loaded into the Channel A TxFIFO.

6. The last character will be transmitted and OPR [0] will be reset one bit time after the last stop bit, causing RTSAN to be negated.

Page 29

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

MR2A [4]—Channel A Clear-to-Send Control if this bit is 0, CTSAN has no effect on the transmitter. If this bit is a 1, the transmitter checks the state of CTSAN (IPO) each time it is ready to send a character. If IPO is asserted (Low), the character is transmitted. If it is negated (High), the TxDA output remains in the marking state and the transmission is delayed until CTSAN goes low. Changes in CTSAN while a character is being transmitted do not affect the transmission of that character.

MR2A [3:0]—Channel A Stop Bit Length Select this field programs the length of the stop bit appended to the transmitted character.

Stop bit lengths of 9/16 to 1 and 1-9/16 to 2 bits, in increments of 1/16 bit, can be programmed for character lengths of 6, 7, and 8 bits. For a character length of 5 bits, 1-1/16 to 2 stop bits can be programmed in increments of 1/16 bit. In all cases, the receiver only checks for a ‘mark’ condition at the center of the stop bit position (one bit time after the last data bit, or after the parity bit if enabled is sampled).

If an external 1X clock is used for the transmitter, MR2A [3] = 0 selects one stop bit and MR2A [3] = 1 selects two stop bits to be transmitted.

Page 30

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

FP– RXA FIFO PARTITION (TYPICAL FOR ALL FIFOS)

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

The 8 bits describing the page size or top page when page size differs from 256 bytes are used

Defines the “bottom” page size when page is note 256 bytes. For a 300 byte FIFO this would be set to decimal 44 (0x2c) and the corresponding FPPC would be set to 2 pages or binary 01.

FPPC – FIFO PARTITION PAGE COUNT

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

TxA

TxB

RxA

RxB

ÁÁ

БББББББ

00 = 1 pages 01 = 2 pages 10 = 3 pages 11 = 4 pages

ББББББ

00 = 1 pages 01 = 2 pages 10 = 3 pages 11 = 4 pages

ББББББ

00 = 1 pages 01 = 2 pages 10 = 3 pages 11 = 4 pages

БББББББ

00 = 1 pages 01 = 2 pages 10 = 3 pages 11 = 4 pages

This register is set to 0x00 at reset. This register will be non zero when one or more FIFOs are greater that 256 bytes

FIL FIFO INTERRUPT LEVEL (TYPICAL FOR ALL FIFOS)

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

The 8 bits describing the level of the bottom page where interrupt arbitration occurs. Normally set to zero

This register is used to control when the FIFO fill level will enter the interrupt arbitration. This is used to improve interrupt efficiency when channels have a large difference in baud rates and to bias the transmitter to be less important that the receiver.

CSRA—Channel A Clock Select Register CSRA [7:4]

Channel A Receiver Clock Select

This field selects the baud rate clock for the Channel A receiver. The field definition is shown in Table 9.

CSR CLOCK SELECT REGISTER

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

CSRA CSRB

RECEIVER CLOCK SELECT

TRANSMITTER CLOCK SELECT

See Text and table 9

Page 31

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Table 9. Baud Rate (Base on a 14.7456MHz crystal clock)

ББББББББББ

MR0[0] = 0 (NORMAL MODE)

MR0[0] = 1 (EXTENDED MODE I)

MR0[2] = 1 (EXTENDED MODE II)

CSRA[7:4]

БББББ

ACR[7] = 0

ACR[7] = 1

ACR[7] = 0

ACR[7] = 1

ACR[7] = 0

ACR[7] = 1

0000

БББББ

300

450

4,800

7,200

0001

БББББ

110

880

0010

БББББ

134.5

1,076

0011

БББББ

200

150

1200

900

19.2K

14.4K

0100

БББББ

300

1800

28.8K

0101

БББББ

600

3600

57.6K

0110

БББББ

1,200

7200

7,200

115.2K

0111

БББББ

1,050

2,000

1,050

2,000

1,050

2,000

1000

БББББ

2,400

14.4K

57.6K

1001

БББББ

4,800

28.8K

4,800

1010

БББББ

7,200

1,800

7,200

1,800

57.6K

14.4K

1011

БББББ

9,600

57.6K

9,600

1100

38.4K

19.2K

230.4K

115.2K

38.4K

19.2K

1101

БББББ

Timer

1110

БББББ

*** I/O? IP4–16X

IP4–16X

1111

БББББ

IP4–1X

NOTE:

The receiver clock is always a 16X clock except for CSRA [7:4] = 111 1.

CSRA [3:0]—Channel A Transmitter Clock Select

This field selects the baud rate clock for the Channel A transmitter. The field definition is as shown in Table 9, except as follows:

CSRA[3:0]

ACR[7] = 0

ACR[7] = 1

1110

1111

IP3–16X

IP3–1X

IP3–16X

IP3–1X

The transmitter clock is always a 16X clock except for CSR [3:0] = 111 1.

CSRB—Channel B Clock Select Register

CSRB [7:4]—Channel B Receiver Clock Select

This field selects the baud rate clock for the Channel B receiver. The field definition is as shown in Table 9, except as follows:

CSRB [7:4]

ACR[7] = 0

ACR[7] = 1

1110

1111

IP6–16X

IP6–1X

IP6–16X

IP6–1X

The receiver clock is always a 16X clock except for CSRB [7:4] = 111 1.

CSRB [3:0]—Channel B Transmitter Clock Select

This field selects the baud rate clock for the Channel B transmitter. The field definition is as shown in Table 9, except as follows:

CSRB [3:0]

ACR[7] = 0

ACR[7] = 1

1110

1111

IP5–16X

IP5–1X

IP5–16X

IP5–1X

The transmitter clock is always a 16X clock except for CSRB [3:0] = 111 1.

Page 32

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Table 10. CR - Command Register

CR is used to write commands to the Quad UART.

Bits 7:3

Bit 2

Bit 1

Bit 0

Channel Command codes see “Command Register Table”

1 = Hold present condition of Tx & Rx Enables 0 = Change Tx & Rx enable conditions

1 = Enable Tx 0 = Disable Tx

1 = Enable Rx 0 = Disable Rx

CR[2] - Lock TxD and RxFIFO enables

If set, the transmitter and receiver enable bits, CR[1:0] are not significant. The enabled/disabled state of a receiver or transmitter can be changed only if this bit is at zero during the time of the write to the command register. WRITES TO THE UPPER BITS OF THE CR WOULD USUALLY HAVE CR[2] AT 1 to maintain the condition of the receiver and transmitter. The bit provides a mechanism for writing commands to a channel, via CR[7:3], without the necessity of keeping track of or reading the current enable status of the receiver and transmitter.

CR[1] - Enable Transmitter

A one written to this bit enables operation of the transmitter. The TxRDY status bit will be asserted. When disabled by writing a zero to this bit, the command terminates transmitter operation and resets the TxRDY and TxEMT status bits. However, if a character is being transmitted or if characters are loaded in the TxFIFO when the transmitter is disabled, the transmission of the all character(s) is completed before assuming the inactive state.

CR[0] - Enable Receiver

A one written to this bit enables operation of the receiver. If not in the special Wake-up mode, this also forces the receiver into the search for start bit state. If a zero is written, this command terminates operation of the receiver immediately - a character being received will be lost. The command has no effect on the receiver status bits or any other control registers. If the special wake-up mode is programmed, the receiver operates even if it is disabled (see Wake-up Mode).

CR[7:3] - Miscellaneous Commands (See Table below) The encoded value of this field can be used to specify a single command as follows: 00000 No command. 00001 Reserved. 00010 Reset receiver. Resets the receiver as if a hardware reset

had been applied. The receiver is disabled and the FIFO pointer is reset to the first location effectively discarding all unread characters in the FIFO.

00011 Reset transmitter. Resets the transmitter as if a hardware

reset had been applied.

00100 Reset error status. Clears the received break, parity error,

framing error, and overrun error bits in the status register (SR[7:4]). Used in character mode to clear overrun error status (although RB, PE and FE bits will also be cleared), and in block mode to clear all error status after a block of data has been received.

00101 Reset break change interrupt. Causes the break detect

change bit in the interrupt status register (ISR[2]) to be cleared to zero.

00110 Start break. Forces the TxD output low (spacing). If

the transmitter is empty, the start of the break condition will be delayed up to two bit times. If the transmitter is active, the break begins when transmission of the current character is completed. If there are characters in the TxFIFO, the start of break is delayed until those characters, or any others loaded after it have been transmitted (TxEMT must be true before break begins). The transmitter must be enabled to start a break.

00111 Stop break. The TxD line will go high (marking) within two

bit times. TxD will remain high for one bit time before the next character, if any, is transmitted.

01000 Assert RTSN. Causes the RTSN output to be asserted

(low).

01001 Negate RTSN. Causes the RTSN output to be negated

(high).

Note: The two commands above actually reset and set, respectively, the I/O2 or I/O1 pin associated with the I/OPIOR register.

01010 Reserved. 01011 Reserved. 01100 Reserved. 01101 Block error status mode. Upon reset of the device or an

individual receiver, the block mode of receiver error status accumulates as each character moves to the bottom of the RxFIFO, the position from which it will be read. In this mode of operation, the RxFIFO may contain a character with non-zero error status for some time. The status will not reflect the error character’s presence until it is ready to be popped from the RxFIFO. Command 01101 allows the error status to be updated as each character is pushed into the RxFIFO. This allows the earliest detection of a problem character, but complicates the determination of exactly which character is causing the error. This mode of block error accumulation may be

exited only by resetting the chip or the individual receiver. 0111 1 Reserved. 10000 Transmit an Xon Character 10001 Transmit an Xoff Character 10010 Reserved for channels b-d, for channel a: enables a Gang

Write of Xon Character Registers. After this command is

issued, a write to the channel A Xon Character Register

will result in a write to all channel’s Xon character

registers. This command provides a mechanism to

initialize all the Xon Character registers with one write. A

write to channel A Xon Character Register returns the

Quad UART to the individual Xon write mode. 10011 Reserved for channels b-d, for channel a: enables Gang

Write of Xoff Character Registers. After this command is

issued, a write to the channel A Xoff Character Register

will result in a write to all channel’s Xoff character

registers. This command provides a mechanism to

initialize all the Xoff Character registers with one write. A

write to channel A Xoff Character Register returns the

Quad UART to the individual Xoff write mode.

Note: Gang writing of Xon/Xoff Character Commands: Issuing command causes the next write to Xon/Xoff Character Register A to effect a simultaneous write into the other 3 Xon/Xoff character registers. After the Xon/Xoff Character Register A is written, the 28L194 returns to individual write mode for the Xon/Xoff Character Registers. Other intervening reads and writes are ignored. The device resets to individual write mode.

10100 Reserved for channels b-d, for channel a: executes a

Gang Load of Xon Character Registers. Executing this

command causes a write of the value x’11 to all channel’s

Xon character registers. This command provides a

mechanism to initialize all the Xon Character registers to

Page 33

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

a default value with one write. Execution of this command is immediate and does not effect the timing of subsequent host I/O operations.

10101 Reserved for channels b-d, for channel a: executes a

Gang Load of Xoff Character Registers. Executing this command causes a write of the value x’13 to all channel’s Xoff character registers. This command provides a mechanism to initialize all the Xoff Character registers to a default value with one write. Execution of this command is immediate and does not effect the timing of subsequent host I/O operations.

10110 Xoff resume command (CRXoffre; not active in

“Auto-Transmit Mode”). A command to cancel a previous Host Xoff command. Upon receipt, the channel’s transmitter will transfer a character, if any, from the TxFIFO and begin transmission.

10111 Host Xoff command (CRXoff). This command allows tight

host CPU control of the flow control of the channel transmitter. When interrupted for receipt of an Xof f character by the receiver, the host may stop transmission of further characters by the channel transmitter by issuing the Host Xoff command. Any character that has been transferred to the TxD shift register will complete its transmission, including the stop bit.

11000 Cancel Host transmit flow control command. Issuing this

command will cancel a previous transmit command if the

flow control character is not yet loaded into the TxD Shift

or if its transmission has already begun, then this

command has no effect. 11001-11011

Reserved. 11011 Reset Address Recognition Status. This command clears

the interrupt status that was set when an address

character was recognized by a disabled receiver

operating in the special mode. 11100-1 1101

Reserved. 11110 Resets all UART channel registers. This command

provides a means to zero all the UART channels that

are not reset to x’00 by a reset command or a hardware

reset. 11111 Reserved for channels b-d, for channel a: executes a chip

wide reset. Executing this command in channel a is

equivalent to a hardware reset with the RESETN pin.

Executing command register reset in channel b-d, has no

effect.

Table 11. Command Register Code

Commands x’12, x13, x’14, x’15, x’1f (marked with*) are global and exist only in channel A ’s register space.

ÁÁÁÁ

Channel Command

Code

ББББББББ

Channel

Command

БББББ

Channel Command

Code

ББББББББББББББ

БББББББББББББ

Channel

Command

CR[7:3]

Description

CR[7:3]

Description

00000

NOP

10000

ББББББББББББББ

Transmit Xon

00001

Reserved

10001

ББББББББББББББ

Transmit Xoff

00010

Reset Receiver

10010

ББББББББББББББ

Gang Write Xon Character Registers *

00011

Reset Transmitter

10011

ББББББББББББББ

Gang Write Xoff Character Registers *

00100

Reset Error Status

10100

Gang Load Xon Character Registers DC1 *

00101

Reset Break Change Interrupt

10101

ББББББББББББББ

Gang Load Xoff Character Registers DC3 *

00110

Begin Transmit Break

10110

ББББББББББББББ

Xoff Resume Command

00111

End Transmit Break

10111

ББББББББББББББ

Host Xoff Command

01000

Assert RTSN (I/O2 or I/O1)

11000

ББББББББББББББ

Cancel Transmit X Char command

01001

Negate RTSN (I/O2 or I/O1)

11001

Reserved

01010

Set time-out mode on

11010

ББББББББББББББ

Reserved

01011

Reserved

11011

ББББББББББББББ

Reset Address Recognition Status

01100

Set time-out mode off

11100

ББББББББББББББ

Reserved

01101

Block Error Status configure

11101

ББББББББББББББ

Reserved

01110

Reserved

11110

Reset All UART channel registers

01111

Reserved

11111

ББББББББББББББ

Reset Device *

Page 34

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

SRA—Channel A Status Register

SR STATUS REGISTER

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

ÁÁ

SRA SRB

ÁÁÁ

RECEIVED

BREAK

ÁÁÁ

FRAMING

ERROR

ÁÁ

PARITY

ERROR

ÁÁÁ

OVERRUN

ERROR

ÁÁÁ

TxEMT

ÁÁ

TxRDY

ÁÁÁ

FFULL

ÁÁÁ

RxRDY

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

0 = No

1 = Yes

NOTE:

1. These status bits are appended to the corresponding data character in the receive FIFO. A read of the status provides these bits (7:5) from the top of the FIFO together with bits (4:0). These bits are cleared by a “reset error status” command. In character mode they are discarded when the corresponding data character is read from the FIFO. In block error mode, the error-reset command (command 4x or receiver reset )must used to clear block error conditions

SRA [7]—Channel A Received Break this bit indicates that an all zero character of the programmed length has been received without a stop bit. Only a single FIFO position is occupied when a break is received: further entries to the FIFO are inhibited until the RxDA line returns to the marking state for at least one-half a bit time two successive edges of the internal or external 1X clock. This will

usually require a high time of one X1 clock period or 3 X1 edges since the clock of the controller is not synchronous to the X1 clock.

When this bit is set, the Channel A ‘change in break’ bit in the ISR (ISR [2]) is set. ISR [2] is also set when the end of the break condition, as defined above, is detected.

The break detect circuitry can detect breaks that originate in the middle of a received character. However, if a break begins in the middle of a character, it must persist until at least the end of the next character time in order for it to be detected.

This bit is reset by command 4 (0100) written to the command register or by receiver reset.

SRA [6]—Channel A Framing Error

This bit, when set, indicates that a stop bit was not detected when the corresponding data character in the FIFO was received. The stop bit check is made in the middle of the first stop bit position.

SRA [5]—Channel A Parity Error

This bit is set when the ‘with parity’ or ‘force parity’ mode is programmed and the corresponding character in the FIFO was received with incorrect parity.

In the special multi-drop mode the parity error bit stores the receive A/D (Address/Data) bit.

SRA [4]—Channel A Overrun Error

This bit, when set, indicates that one or more characters in the received data stream have been lost. It is set upon receipt of a new character when the FIFO is full and a character is already in the receive shift register waiting for an empty FIFO position. When this occurs, the character in the receive shift register (and its break detect, parity error and framing error status, if any) is lost.

This bit is cleared by a ‘reset error status’ command.

SRA [3]—Channel A Transmitter Empty (TxEMTA)

This bit will be set when the transmitter under runs, i.e., both the TxEMT and TxRDY bits are set. This bit and TxRDY are set when the transmitter is first enabled and at any time it is re-enabled after either (a) reset, or (b) the transmitter has assumed the disabled state. It is always set after transmission of the last stop bit of a character if no character is in the THR awaiting transmission.

It is reset when the THR is loaded by the CPU, a pending transmitter disable is executed, the transmitter is reset, or the transmitter is disabled while in the under run condition.

SRA [2]—Channel A Transmitter Ready (TxRDYA)

This bit, when set, indicates that the transmit FIFO is not full and ready to be loaded with another character. This bit is cleared when the transmit FIFO is loaded by the CPU and there are (after this load) no more empty locations in the FIFO. It is set when a character is transferred to the transmit shift register. TxRDYA is reset when the transmitter is disabled and is set when the transmitter is first enabled. Characters loaded to the TxFIFO while this bit is 0 will be lost. This bit has different meaning from ISR [0].

SRA [1]—Channel A FIFO Full (FFULLA)

This bit is set when a character is transferred from the receive shift register to the receive FIFO and the transfer causes the FIFO to become full, i.e., all eight FIFO positions are occupied. It is reset when the CPU reads the receive FIFO. If a character is waiting in the receive shift register because the FIFO is full, FFULLA will not be reset when the CPU reads the receive FIFO. This bit has different meaning from ISR(1) when MR1 6 is programmed to a ‘1’.

SRA [0]—Channel A Receiver Ready (RxRDY A)

This bit indicates that a character has been received and is waiting in the FIFO to be read by the CPU. It is set when the character is transferred from the receive shift register to the FIFO and reset when the CPU reads the receive FIFO, only if (after this read) there are no more characters in the FIFO.

SRB—Channel B Status Register

The bit definitions for this register are identical to the bit definitions for SRA, except that all status applies to the Channel B receiver and transmitter and the corresponding inputs and outputs.

Page 35

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

OPCR—Output Port Configuration Register OPCR OUTPUT PORT CONFIGURA TION REGISTER

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

OP7

OP6

OP5

OP4

OP3

OP2

OP1

OP0

ÁÁ

0 = OPR[7] 1 = TxRDY B

ÁÁÁ

0 = OPR[6] 1 = TxRDY A

БББББ

0 = OPR[5] 1 = RxRDY/FFULL B

БББББ

0 = OPR[4] 1 = RxRDY/FFULL A

ÁÁÁÁ

00 = OPR[3] 01 = C/T OUTPUT 10 = TxCB(1X) 11 = RxCB(1X)

БББББ

00 = OPR[2] 01 = TxCA(16X) 10 = TxCA(1X) 11 = RxCA(1X)

OPCR [7]—OP7 Output Select

This bit programs the OP7 output to provide one of the following: 0 The complement of OPR [7]. 1 The Channel B transmitter interrupt output which is

the complement of ISR [4]. When in this mode OP7 acts as an open-drain output. Note that this output is not masked by the contents of the IMR.

OPCR [6]—OP6 Output Select

This bit programs the OP6 output to provide one of the following: 0 The complement of OPR [6]. 1 The Channel A transmitter interrupt output which is

the complement of ISR [0]. When in this mode OP6 acts as an open-drain output. Note that this output is not masked by the contents of the IMR.

OPCR [5]—OP5 Output Select

This bit programs the OP5 output to provide one of the following: 0 The complement of OPR [5]. 1 The Channel B receiver interrupt output which is

the complement of ISR [5]. When in this mode OP5 acts as an open-drain output. Note that this output is not masked by the contents of the IMR.

OPCR [4]—OP4 Output Select

This field programs the OP4 output to provide one of the following: 0 The complement of OPR [4]. 1 The Channel A receiver interrupt output which is

the complement of ISR [1]. When in this mode OP4 acts as an open-drain output. Note that this output is not masked by the contents of the IMR.

OPCR [3:2]—OP3 Output Select

This bit programs the OP3 output to provide one of the following:

00 The complement of OPR [3]. 01 The counter/timer output, in which case OP3 acts

as an open-drain output. In the timer mode, this output is a square wave at the programmed frequency. In the counter mode, the output remains high until terminal count is reached; at which time it goes low. The output returns to the high state when the counter is stopped by a stop counter command. Note that this output is not masked by the contents of the IMR.

10 The 1X clock for the Channel B transmitter, which is

the clock that shifts the transmitted data. If data is not being transmitted, a free running 1X clock is output.

11 The 1X clock for the Channel B receiver, which is

the clock that samples the received data. If data is not being received, a free running 1X clock is output.

OPCR [1:0]—OP2 Output Select

This field programs the OP2 output to provide one of the following: 00 The complement of OPR [2]. 01 The 16X clock for the Channel A transmitter.

This is the clock selected by CSRA [3:0], and will be a 1X clock if CSRA [3:0] = 111 1.

10 The 1X clock for the Channel A transmitter, which is

the clock that shifts the transmitted data. If data is not being transmitted, a free running 1X clock is output.

11 The 1X clock for the Channel A receiver, which is

the clock that samples the received data. If data is not being received, a free running 1X clock is output.

Page 36

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

SOPR—Set the Output Port Bits (OPR)

SOPR [7:0]—Ones in the byte written to this register will cause the corresponding bit positions in the OPR to set to 1. Zeros have no effect. This allows software to set individual bits with our keeping a copy of the OPR bit configuration.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

ÁÁÁÁ

BIT 2

BIT 1

BIT 0

Set OPR Bits

OP 7

OP 6

OP 5

OP 4

OP 3

ÁÁÁÁ

OP 2

OP 1

OP 0

1 = set bit 0 = no change

ÁÁÁÁ

1 = set bit 0 = no change

ROPR—Reset Output Port Bits (OPR)

ROPR [7:0]—Ones in the byte written to the ROPR will cause the corresponding bit positions in the OPR to set to 0. Zeros have no effect. This allows software to reset individual bits with our keeping a copy of the OPR bit configuration.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

Reset OPR Bits

OP 7

OP 6

OP 5

OP 4

OP 3

OP 2

OP 1

OP 0

ÁÁÁÁÁÁÁ

1 = reset bit 0 = no change

ÁÁ

1 = reset bit 0 = no change

ÁÁÁ

1 = reset bit 0 = no change

ÁÁ

1 = reset bit 0 = no change

ÁÁÁ

1 = reset bit 0 = no change

ÁÁ

1 = reset bit 0 = no change

ÁÁÁ

1 = reset bit 0 = no change

ÁÁÁ

1 = reset bit 0 = no change

OPR Output Port Register

The output pins (OP pins) drive the compliment of the data written to this register.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

OPR

OP 7

OP 6

OP 5

OP 4

OP 3

OP 2

OP 1

OP 0

0 = Pin High

1 = Pin Low

0 = Pin High

1 = Pin Low

0 = Pin High

1 = Pin Low

0 = Pin High

1 = Pin Low

0 = Pin High

1 = Pin Low

0 = Pin High

1 = Pin Low

0 = Pin High

1 = Pin Low

0 = Pin High

1 = Pin Low

ACR Auxiliary Control Register

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

ACR

BRG SET

Select

Counter Timer Mode

Mode and clock sour select

Delta

IP3 int enable

Delta

IP3 int enable

Delta

IP3 int enable

Delta

IP3 int enable

ÁÁÁÁÁÁ

0 = set 1 1 = set 2

ББББББББББ

See table 12

ÁÁÁ

0 = off

1 = enabled

ÁÁ

0 = off

1 = enabled

ÁÁÁ

0 = off

1 = enabled

ÁÁÁ

0 = off

1 = enabled

ACR—Auxiliary Control Register

ACR [7]—Baud Rate Generator Set Select

This bit selects one of two sets of baud rates to be generated by the BRG (See Table 9).

The selected set of rates is available for use by the Channel A and B receivers and transmitters as described in CSRA and CSRB. Baud rate generator characteristics are given in Table 9?.

ACR [6:4]—Counter/Timer Mode And Clock Source Select

This field selects the operating mode of the counter/timer and its clock source as shown in Table 12.

ACR [3:0]—IP3, IP2, IP1, IP0 Change-of-State Interrupt Enable

This field selects which bits of the input port change register (IPCR) cause the input change bit in the interrupt status register (ISR [7]) to be set. If a bit is in the ‘on’ state the setting of the corresponding bit in the IPCR will also result in the setting of ISR [7], which results in the generation of an interrupt output if IMR [7] = 1. If a bit is in the ‘off’ state, the setting of that bit in the IPCR has no effect on ISR [7].

Table 12. ACR 6:4 Field Definition

ACR 6:4

MODE

CLOCK SOURCE

000

Counter

External (IP2)

001

Counter

TxCA – 1X clock of Channel A transmitter

010

Counter

TxCB – 1X clock of Channel B transmitter

ÁÁ

011

Counter

ББББББББББ

Crystal or external clock (X1/CLK) divided by 16

100

Timer

External (IP2)

101

Timer

External (IP2) divided by 16

110

Timer

Crystal or external clock (X1/CLK)

111

Timer

Crystal or external clock (X1/CLK) divided by 16

NOTE:

The timer mode generates a square wave.

Page 37

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Table 13. I/OPCR3–0 (Ports 3–0)

Bits 7:6

Bits 5:4

Bits 3:2

БББББББББ

Bits 1:0

I/O3 control

I/O2 control

I/O1 control

БББББББББ

I/O0 control

БББББББ

00 - General purpose input 01 - OPR[3] output 10 - Tx interrupt 11 - Reserved

БББББББ

00 - General purpose input 01 - OPR[2] output 10 - Rx interrupt 11 - Reserved

ББББББББ

00 - General purpose input 01 - OPR[1] output 10 - CTS 11 - Reserved

БББББББББ

БББББББ

00 - General purpose input 01 - OPR[0] output 10 - RTS 11 - Reserved

Table 14. I/OPCR7–4 (Ports 7–4)

Bits 7:6

Bits 5:4

Bits 3:2

БББББББББ

Bits 1:0

I/O3 control

I/O2 control

I/O1 control

БББББББББ

I/O0 control

БББББББ

00 - General purpose input 01 - OPR[7] output 10 - DMA TX 11 - Reserved

БББББББ

00 - General purpose input 01 - OPR[6] output 10 - DMA RX 11 - Reserved

ББББББББ

00 - General purpose input 01 - OPR[5] output 10 - DSR 11 - Reserved

БББББББББ

БББББББ

00 - General purpose input 01 - OPR[5] output 10 - DTR 11 - Reserved

Page 38

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Table 15. ISR - Interrupt Status Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

ÁÁ

I/O Port change of state

ÁÁ

Receiver Watch-dog Time-out

ÁÁÁÁ

Address recognition event

Xon/off event

ÁÁÁ

Always 0

ÁÁÁ

Change of Break State

ÁÁÁÁ

RxRDY Receiver has entered arbitration process

ББББББ

TxRDY Transmitter has entered arbitration process

This register provides the status of all potential interrupt sources for a UART channel. When generating an interrupt arbitration value, the contents of this register are masked by the interrupt mask register (IMR). If a bit in the ISR is a ’1’ and the corresponding bit in the IMR is also a ’1’, interrupt arbitration for this source will begin. If the corresponding bit in the IMR is a zero, the state of the bit in the ISR can have no affect on the IRQN output. Note that the IMR may or may not mask the reading of the ISR as determined by MR1[6]. If MR1[6] is cleared, the reset and power on default, the ISR is read without modification. If MR1[6] is set, the a read of the ISR gives a value of the ISR ANDed with the IMR.

ISR[7] - Input Change of State

This bit is set when a change of state occurs at the I/O1 or I/O0 input pins. It is reset when the CPU reads the Input Port Register, IPR.

ISR[6] Watch-dog Time-out

This bit is set when the receiver’s watch-dog timer has counted more than 64 bit times since the last RxFIFO event. RxFIFO events are a read of the RxFIFO or GRxFIFO, or the push of a received character into the FIFO. The interrupt will be cleared automatically upon the push of the next character received or when the RxFIFO or GRxFIFO is read. The receiver watch-dog timer is included to allow detection of the very last characters of a received message that may be waiting in the RxFIFO, but are too few in number to successfully initiate an interrupt. Refer to the watch-dog timer description for details of how the interrupt system works after a watch-dog time-out.

ISR[5] - Address Recognition Status Change

This bit is set when a change in receiver state has occurred due to an Address character being received from an external source and comparing to the reference address in ARCR. The bit and interrupt is negated by a write to the CR with command x11011, Reset Address Recognition Status.

ISR[4] - Xon/Xoff Status Change

This bit is set when an Xon/Xoff character being received from an external source. The bit is negated by a read of the channel Xon Interrupt Status Register, XISR.

ISR[3] - Reserved Always reads a 0 ISR[2] - Change in Channel Break Status

This bit, when set, indicates that the receiver has detected the beginning or the end of a received break. It is reset when the CPU issues a reset break change interrupt command via the CR.

ISR[1] - Receiver Ready

The general function of this bit is to indicate that the RxFIFO has data available. The particular meaning of this bit is programmed by MR2[3:2]. If programmed as receiver ready(MR2[3:2] = 00), it indicates that at least one character has been received and is waiting in the RxFIFO to be read by the host CPU. It is set when the character is transferred from the receive shift register to the RxFIFO and reset when the CPU reads the last character from the RxFIFO.

If MR2[3:2] is programmed as FIFO full, ISR[1] is set when a character is transferred from the receive holding register to the RxFIFO and the transfer causes the RxFIFO to become full, i.e. all FIFO positions are occupied. It is reset when ever RxFIFO is not full. If there is a character waiting in the receive shift register because the FIFO is full, the bit is set again when the waiting character is transferred into the FIFO.

The other two conditions of these bits, 3/4 and half full operate in a similar manner. The ISR[1] bit is set when the RxFIFO fill level meets or exceeds the value; it is reset when the fill level is less. See the description of the MR2 register.

Note: This bit must be at a one (1) for the receiver to enter the arbitration process. It is the fact that this bit is zero (0) when the RxFIFO is empty that stops an empty FIFO from entering the interrupt arbitration. Also note that the meaning if this bit is not quite the same as the similar bit in the status register (SR).

ISR[0] - Transmitter Ready

The general function of this bit is to indicate that the TxFIFO has an at least one empty space for data. The particular meaning of the bit is controlled by MR0[5:4] indicates the TxFIFO may be loaded with one or more characters. If MR0[5:4] = 00 (the default condition) this bit will not set until the TxFIFO is empty - all FIFO bytes available. If the fill level of the TxFIFO is below the trigger level programmed by the TxINT field of the Mode Register 0, this bit will be set. A one in this position indicates that at least one character can be sent to the TxFIFO. It is turned off as the TxFIFO is filled above the level programmed by MR0[5:4. This bit turns on as the FIFO empties; the RxFIFO bit turns on as the FIFO fills. This often a point of confusion in programming interrupt functions for the receiver and transmitter FIFOs.

Note: This bit must be at a one (1) for the transmitter to enter the arbitration process. It is the fact that this bit is zero (0) when the RxFIFO is full that stops a full FIFO from entering the interrupt arbitration. Also note that the meaning if this bit is not quite the same as the similar bit in the status register (SR).

Page 39

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Table 16. IMR - Interrupt Mask Register

Bit 7

Bit 6

Bit 5

Bit 4

ÁÁÁ

Bit 3

Bit 2

Bit 1

Bit 0

ÁÁÁ

I/O Port change of state

БББББ

Receiver Watch-dog Time-out

ÁÁÁÁ

Address recognition event

ÁÁÁ

Xon/off event

ÁÁÁ

Set to 0

ÁÁÁ

Change of Break State

ÁÁÁ

RxRDY interrupt

ÁÁÁ

TxRDY interrupt

The programming of this register selects which bits in the ISR cause an interrupt output. If a bit in the ISR is a ’1’ and the corresponding bit in the IMR is a ’1’, the interrupt source is presented to the internal interrupt arbitration circuits, eventually resulting in the IRQN output being asserted (low). If the corresponding bit in the IMR is a zero, the state of the bit in the ISR has no affect on the IRQN output.

IMR[7] - Controls if a change of state in the inputs equipped with input change detectors will cause an interrupt.

IMR[6] - Controls the generation of an interrupt by the watch-dog timer event. If set, a count of 64 idle bit times in the receiver will begin interrupt arbitration.

IMR[5] - Enables the generation of an interrupt in response to changes in the Address Recognition circuitry of the Special Mode (multi-drop or wake-up mode).

IMR[4] - Enables the generation of an interrupt in response to recognition of an in-band flow control character.

IMR[3] - Reserved IMR[2] - Enables the generation of an interrupt when a Break

condition has been detected by the channel receiver. IMR[1] - Enables the generation of an interrupt when servicing for

the RxFIFO is desired. IMR[0] - Enables the generation of an interrupt when servicing for

the TxFIFO is desired.

Page 40

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Table 17. XISR - Xon-Xoff Interrupt Status Register

See MR0 for a description of enabling these functions

Bits 7:6

Bits 5:4

Bits 3:2

Bits 1:0

Received X Character Status

Automatic X Character transmission status

TxD flow status

TxD character status

ББББББ

00 - none 01 - Xoff received 10 - Xon received 11 - both received

ББББББББ

00 - none 01 - Xon transmitted 10 - Xoff transmitted 11 - Illegal, does not occur

ББББББ

00 - normal 01 - TxD halt pending 10 - re-enabled 11 - flow disabled

БББББББББ

00 - normal TxD data 01 - wait on normal data 10 - Xoff in pending 11 - Xon in pending

NOTE: Bits of this register may be cleared by a read of the register. XISR[7:6] - Received X Character Status. This field can be read to

determine if the receiver has encountered an Xon or Xoff character in the incoming data stream. These bits are maintained until a read of the XISR. The field is updated by X character reception regardless of the state of MR0(7, 3:2) or IMR(4). The field can therefore be used as a character detector for the bit patterns stored in the Xon and Xoff Character Registers.

XISR[5:4] - Automatic transmission Status. This field indicates the last flow control character sent in the Auto Receiver flow control mode. If Auto Receiver mode has not been enabled, this field will always read b’00. It will likewise reset to b’00 if MR0(3) is reset. If the Auto Receiver mode is exited while this field reads b’10, it is the user’s responsibility to transmit an Xon, when appropriate.

XISR[3:2] - TxD flow Status. This field tracks the transmitter’s flow status as follows:

00 - normal. The flow control is under host control. 01 - TxD halt pending. After the current character finishes the

transmitter will stop. The status will then change to b’00. 10 - re-enabled. The transmitter had been halted and restarted. It

is sending data characters. After a read of the XISR, it will return to “normal” status.

11 - disabled. The transmitter is flow controlled.

XISR[1:0] - TxD character Status. This field allows determination of the type of character being transmitted. If XISR(1:0) is b’01, the channel is waiting for a data character to transfer from the TxFIFO. This condition will only occur for a bit time after an Xon or Xoff character transmission unless the TxFIFO is empty.

Page 41

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

CTPU and CTPL—Counter/Timer Registers

CTPU COUNTER TIMER PRESET UPPER

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

CTPU

The lower eight (8) bits for the 16 bit counter timer preset register

CTPL COUNTER -TIMER PRESET LOW

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

CTPL

The Upper eight (8) bits for the 16 bit counter timer preset register

The CTPU and CTPL hold the eight MSBs and eight LSBs, respectively, of the value to be used by the counter/timer in either the counter or timer modes of operation. The minimum value that may be loaded into the CTPU/CTPL registers is H‘0002’. Note that these registers are write-only and cannot be read by the CPU.

In the timer mode, the C/T generates a square wave whose period is twice the value (in C/T clock periods) of the CTPU and CTPL. The waveform so generated is often used for a data clock. The formula for calculating the divisor n to load to the CTPU and CTPL for a particular 1X data clock is shown below.

n = (C/T Clock Frequency) divided by (2 x 16 x Baud rate desired) n = (C/T Clock Frequency)/ (2 x 16 x Baud rate desired)

Often this division will result in a non-integer number, 26.3 for

example. One can only program integer numbers in a digital divider.

Therefore, 26 would be chosen. This gives a baud rate error of

0.3/26.3, which is 1.14% and well within the ability asynchronous

mode of operation. If the value in CTPU and CTPL is changed, the current half-period

will not be affected, but subsequent half periods will be. The C/T will not be running until it receives an initial ‘Start Counter’ command (read at address A3–A0 = 1110). After this, while in timer mode, the C/T will run continuously. Receipt of a start counter command (read with A3–A0 = 1110) causes the counter to terminate the current timing cycle and to begin a new cycle using the values in CTPU and CTPL.

The counter ready status bit (ISR [3]) is set once each cycle of the square wave. The bit is reset by a stop counter command (read with A3–A0 = 0xF). The command however, does not stop the C/T. the generated square wave is output on OP3 if it is programmed to be the C/T output. In the counter mode, the value C/T loaded into CTPU and CTPL by the CPU is counted down to 0. Counting begins upon receipt of a start counter command. Upon reaching terminal count H‘0000’, the counter ready interrupt bit (ISR [3]) is set. The counter continues counting past the terminal count until stopped by the CPU. If OP3 is programmed to be the output of the C/T, the output remains high until terminal count is reached; at which time it goes low. The output returns to the High State and ISR [3] is cleared when the counter is stopped by a stop counter command.

The CPU may change the values of CTPU and CTPL at any time, but the new count becomes effective only on the next start counter commands. If new values have not been loaded, the previous count values are preserved and used for the next count cycle

In the counter mode, the current value of the upper and lower 8 bits of the counter (CTU, CTL) may be read by the CPU. It is recommended that the counter be stopped when reading to prevent potential problems that may occur if a carry from the lower 8 bits to the upper 8 bits occurs between the times that both halves of the counter are read. However, note that a subsequent start counter command will cause the counter to begin a new count cycle using the values in CTPU and CTPL. When the C/T clock divided by 16 is selected, the maximum divisor becomes 1,048,575.

The CTS, RTS, CTS Enable Tx signals

CTS (Clear To Send) is usually meant to be a signal to the transmitter meaning that it may transmit data to the receiver. The CTS input is on pin IP0 for TxA and on IP1 for TxB. The CTS signal is active low; thus; it is called CTSAN for TxA and CTSBN for TxB. RTS is usually meant to be a signal from the receiver indicating that the receiver is ready to receive data. It is also active low and is, thus, called RTSAN for RxA and RTSBN for RxB. RTSAN is on pin OP0 and RTSBN is on OP1. A receiver’s RTS output will usually be connected to the CTS input of the associated transmitter. Therefore, one could say that RTS and CTS are different ends of the same wire!

MR2 (4) is the bit that allows the transmitter to be controlled by the CTS pin (IP0 or IP1). When this bit is set to one AND the CTS input is driven high, the transmitter will stop sending data at the end of the present character being serialized. It is usually the RTS output of the receiver that will be connected to the transmitter’s CTS input. The receiver will set RTS high when the receiver FIFO is full AND the start bit of the ninth character is sensed. Transmission then stops with nine valid characters in the receiver. When MR2 (4) is set to one, CTSN must be at zero for the transmitter to operate. If MR2 (4) is set to zero, the IP pin will have no effect on the operation of the transmitter. MR1 (7) is the bit that allows the receiver to control OP0. When the receiver controls OP0 (or OP1), the meaning of that pin will be.

RESETN

RES

SD00133

Figure 2.

Page 42

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

A0–A3

CEN

RDN

RWD

D0–D7

(READ)

FLOAT FLOATVALID

NOT

VALID

WDN

RWD

VALID

D0–D7

(WRITE)

SD00087

Figure 3.

(b) OUTPUT PINS

RDN

IP0–IP6

WRN

OP0–OP7

OLD DATA NEW DATA

(a) INPUT PINS

SD00135

Figure 4.

Page 43

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

NOTES:

1. INTRN or OP3-OP7 when used as interrupt outputs.

2. The test for open-drain outputs is intended to guarantee switching of the output transistor. Measurement of this response is referenced from the midpoint of the switching signal, V

, to a point 0.5V above VOL. This point represents noise margin that assures true switching has occurred. Beyond this level, the effects of external circuitry and

test environment are pronounced and can greatly affect the resultant measurement.

+0.5V

WRN

INTERRUPT

OUTPUT

+0.5V

RDN

INTERRUPT

OUTPUT

SD00136

Figure 5.

C1 = C2 ∼ 24pF FOR CL = 20pF

CLK

CTC

X1/CLK

CTCLK

RxC

TxC

CLK

CTC

+5V

470Ω

X2*

CLK

*NOTE: X2 MUST BE LEFT OPEN.

3.6864MHz

SC26C92

NOTE: RESISTOR REQUIRED FOR TTL INPUT.

TO UART CIRCUIT

50kΩ to 100kΩ

3pF

C1 and C2 should be chosen according to the crystal manufacturer’s specification. C1 and C2 values will include any parasitic capacitance of the wiring and X1 X2 pins. Gain at 3.6864MHz: 9 to 13 dB Phase at 3.6864MHz: 272 to 276 degrees.

2pF

4pF

Package capacitance approximately 4pF.

SD00154

Figure 6.

Page 44

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

TXD

TCS

1 BIT TIME

(1 OR 16 CLOCKS)

TxD

TxC

(INPUT)

TxC

(1X OUTPUT)

SD00138

Figure 7.

RXS

RXH

RxC

(1X INPUT)

RxD

SD00139

Figure 8.

TRANSMITTER

ENABLED

TxD D1 D2 D3 D4 D6BREAK

TxRDY

(SR2)

WRN

D1 D8 D9 D10 D12START

BREAK

STOP

BREAK

D11 WILL

NOT BE

WRITTEN TO

THE TxFIFO

CTSN

(IP0)

RTSN

(OP0)

OPR(0) = 1 OPR(0) = 1

NOTES:

1. Timing shown for MR2(4) = 1.

2. Timing shown for MR2(5) = 1.

SD00155

Figure 9.

Page 45

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

D1 D2 D8 D9 D10 D11 D12 D13

RxD

D12, D13 WILL BE LOST DUE TO RECEIVER DISABLE.

RECEIVER

ENABLED

RxRDY

(SR0)

FFULL

(SR1)

RxRDY/

FFULL (OP5)

RDN

STATUS DATA

STATUS DATAD2STATUS DATAD3STATUS DATA

D10

D11 WILL BE LOST DUE TO OVERRUN

OVERRUN

(SR4) RESET BY COMMAND

RTS

(OP0)

OPR(0) = 1

NOTES:

1. Timing shown for MR1(7) = 1.

2. Shown for OPCR(4) = 1 and MR(6) = 0.

SD00156

Figure 10.

TRANSMITTER

ENABLED

TxD

ADD#1

TxRDY

(SR2)

WRN

MR1(4–3) = 11

MR1(2) = 1

BIT 9

D0 0

BIT 9

ADD#2 1

BIT 9

MASTER STATION

ADD#1MR1(2) = 0 D0 MR1(2) = 1 ADD#2

RxD

ADD#1 1

BIT 9

D0 0

BIT 9

ADD#2 1

BIT 9

PERIPHERAL STATION

BIT 9

RECEIVER

ENABLED

RxRDY

(SR0)

RDN/WRN

MR1(4–3) = 11

ADD#1

STATUS DATA

ADD#2

SD00096

Figure 11.

Page 46

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

INTRN

D0–D7

TxDA/B

OP0–OP7

50pF

+5V

2.7K

150pF

+5V

I = 2.4mA V

I = 400µA V

SD00157

Figure 12.

Page 47

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

PLCC44: plastic leaded chip carrier; 44 leads SOT187-2

Page 48

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

QFP44: plastic quad flat package; 44 leads (lead length 1.3 mm); body 10 x 10 x 1.75 mm SOT307-2

Page 49

Philips Semiconductors Objective specification

SC28L202

Dual universal asynchronous receiver/transmitter (DUART)

1998 Oct 05

Definitions

Short-form specification — The data in a short-form specification is extracted from a full data sheet with the same type number and title. For

detailed information see the relevant data sheet or data handbook. Limiting values definition — Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134). Stress above one

or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability.

Application information — Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or modification.

Disclaimers

Life support — These products are not designed for use in life support appliances, devices or systems where malfunction of these products can

reasonably be expected to result in personal injury . Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application.

Right to make changes — Philips Semiconductors reserves the right to make changes, without notice, in the products, including circuits, standard cells, and/or software, described or contained herein in order to improve design and/or performance. Philips Semiconductors assumes no responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless otherwise specified.

Philips Semiconductors 811 East Arques Avenue P.O. Box 3409 Sunnyvale, California 94088–3409 Telephone 800-234-7381

 Copyright Philips Electronics North America Corporation 1998

Date of release: 10-98

Document order number: 9397 750 04467

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Data sheet status

Objective specification

Preliminary specification

Product specification

Product status

Development

Qualification

Production

Definition

[1]

This data sheet contains the design target or goal specifications for product development. Specification may change in any manner without notice.

This data sheet contains preliminary data, and supplementary data will be published at a later date. Philips Semiconductors reserves the right to make chages at any time without notice in order to improve design and supply the best possible product.

This data sheet contains final specifications. Philips Semiconductors reserves the right to make changes at any time without notice in order to improve design and supply the best possible product.

Data sheet status

[1] Please consult the most recently issued datasheet before initiating or completing a design.

Datasheet 28L202A1B, 28L202A1A Datasheet (Philips)

Specifications and Main Features

Frequently Asked Questions

User Manual