NEC UPD72042GT Datasheet

DATA SHEET

MOS INTEGRATED CIRCUIT

PD72042

LSI DEVICES FOR Inter Equipment BusTM (IEBusTM)

PROTOCOL CONTROL

The µPD72042 is a microcomputer peripheral LSI device for IEBus protocol control.

The µPD72042 performs all the processing required for layers 1 and 2 of the IEBus. The devices incorporate large transmission and reception buffers, allowing the microcomputer to perform IEBus operations without interruption. They also contain an IEBus driver and receiver, allowing them to directly connected to the bus directly.

FEATURES

Control of layers 1 and 2 of the IEBus protocol

••

• Support of a multi-master scheme

• Broadcast function

• Two communication modes having different transmission speeds can be selected.

Transmission speed Mode 0 Approx. 3.9 Kbps Mode 1 Approx. 17 Kbps

Microcomputer interface

••

Three-/two-wire serial I/O, Transfer starting with MSB

Program crashes can be detected by means of a

••

watchdog timer.

Low power consumption (standby mode):

••

A (max)

50 Oscillator frequency (fX): 6 MHz

••

• frequency accuracy: ±1.5% Operating voltage: 5 V ±10%

••

Built-in IEBus driver and receiver

●●

●● Transmission and reception buffers

Transmission buffer : 33 bytes, FIFO Reception buffer : 40 bytes, FIFO (capable of

holding more than one frame of reception data.)

ORDERING INFORMATION

Part number Package

PD72042GT 16-pin plastic SOP (9.53 mm (375))

The information in this document is subject to change without notice. Before using this document, please confirm that this is the latest version. Not all devices/types available in every country. Please check with local NEC representative for availability and additional information.

Document No. S14870EJ1V0DS00 (1st edition) Date Published June 2000 N CP(N) Printed in Japan

2000

PIN CONFIGURATION (TOP VIEW)

• 16-pin plastic SOP (9.53 mm (375))

PD72042GT

PD72042

SI(SIO)

SO(NC)

SCK

Note

IRQ

C/D

GND

TEST

RESET

SEL

BUS+

BUS−

Note Parentheses indicate the state corresponding to two-wire serial I/O mode.

DD : Main power supply for IEBus (connected to the VDD pin)

BUS–, BUS+ : IEBus I/O C/D : Command/data switch input CS : Chip select input GND : Ground IRQ : Interrupt request output NC : No connection RESET : Reset input SCK : Serial clock input SEL : Serial mode selection SI : Serial data input SIO : Serial data I/O SO : Serial data output TEST : Test input (connected to the V

DD pin)

VDD : Main power supply XI, XO : System clock

Data Sheet S14870EJ1V0DS00

BLOCK DIAGRAM

XI XO

PD72042

BUS + BUS –

Data link controller

Internal bus

Receiver

Driver

Contention

detection

section

Parity generation

section

Parity detection

section

Filter

Oscillation

control section

Program detection

section

P/S conversion

section

Synchronization

control section

crash

CTR

CMR

WDB

(5 bytes)

TBF

(33 bytes)

STR

FLG

C/D

SCK

(SIO)

Serial I/O control section

(NC)

RDB

(7 bytes)

Test circuit

TEST

Timing

generation

section

RESET AV

Frame data

control section

RBF

(40 bytes)

Remark The pin names in parentheses are used when two-wire serial I/O is selected.

SEL

IRQ

GND

Data Sheet S14870EJ1V0DS00

PD72042

CONTENTS

1. PIN FUNCTIONS............................................................................................................................ 6

1.1 PIN FUNCTIONS ................................................................................................................................... 6

2. IEBus OPERATION ....................................................................................................................... 8

2.1 OVERVIEW .............................................................................................................................................. 8

2.2 IEBus COMMUNICATION PROTOCOL.............................................................................................. 9

2.2.1 Bus Mastership Determination (Arbitration) ............................................................................... 10

2.2.2 Communication Mode ................................................................................................................. 10

2.2.3 Communication Address ............................................................................................................. 1 1

2.2.4 Broadcast..................................................................................................................................... 11

2.3 TRANSMISSION PROTOCOL .............................................................................................................. 11

2.4 TRANSMISSION DATA (CONTENTS OF THE DATA FIELD)........................................................ 17

2.5 BIT FORMAT.......................................................................................................................................... 21

3. MICROCOMPUTER INTERFACE ................................................................................................. 22

3.1 TRANSFER METHOD ........................................................................................................................... 22

3.2 DATA TRANSFER FORMAT................................................................................................................ 23

3.2.1 Three-Wire Data Transfer (SEL = 1) .......................................................................................... 23

3.2.2 Two-Wire Data Transfer (SEL = 0) ............................................................................................. 25

3.3 CONNECTION TO A MICROCOMPUTER ......................................................................................... 27

3.4 STANDBY MODE SETTING AND CANCELLATION ....................................................................... 2 8

3.5 RESET MODE SETTING AND CANCELLATION ............................................................................ 2 8

4. REGISTERS .................................................................................................................................... 29

5. EXAMPLE TIMINGS FOR COMMUNICATION .......................................................................... 59

6. EXAMPLE MICROCOMPUTER PROCESSING FLOW ............................................................. 67

6.1 COMMUNICATION FLAGS ................................................................................................................... 68

6.2 MAIN ROUTINE ..................................................................................................................................... 69

6.3 INTERRUPT ROUTINE ......................................................................................................................... 7 0

6.4 PROCESSING ROUTINES .................................................................................................................... 72

6.4.1

6.4.2 Communication Flag Initialization Routine................................................................................. 72

6.4.3 Command Processing Routine ................................................................................................... 73

6.4.4 Master Communication Processing Routine.............................................................................. 7 3

6.4.5 Slave Data Transmission Processing Routine........................................................................... 77

6.4.6 Transmission Processing Routine .............................................................................................. 80

6.4.7 Reception Processing Routine ................................................................................................... 81

PD72042 Initial Setting Routine ............................................................................................... 72

7. ELECTRICAL CHARACTERISTICS ............................................................................................. 82

8. PACKAGE DRAWING .................................................................................................................... 86

Data Sheet S14870EJ1V0DS00

PD72042

9. RECOMMENDED SOLDERING CONDITIONS........................................................................... 87

APPENDIX A MAIN DIFFERENCES BETWEEN µPD72042, µPD72042B, AND µPD6708 ..... 88

APPENDIX B IEBus PROTOCOL ANALYZER................................................................................ 88

Data Sheet S14870EJ1V0DS00

1. PIN FUNCTIONS

1.1 PIN FUNCTIONS

PD72042

Pin No.

1 2

6 7

8 9

10 11

Note

SCK SI (SIO)

SO (NC)

IRQ

C/D

XI XO

GND BUS–

BUS+ AVDD

SEL

Note

I/O

Input Input (I/O)

Output (none)

Output

Input

–

– I/O

–

Input

Function

Serial clock input pin for CPU interface Serial data pin for CPU interface. (This pin

functions as an input pin when 3-wire serial I/O mode is selected, or as an I/O pin when 2-wire serial I/O mode is selected.)

Serial data output pin for CPU interface. (The pin functions as an output when 3-wire serial I/O mode is selected. When 2-wire serial I/O mode is selected, the pin is left open.)

Output pin for making an interrupt request to the CPU. When a return code or a program crash is detected, a high-level signal is output on this pin for at least 8 µs.

Input pin used to select control mode or data read/write mode. When this pin is driven high, internal register address setting and data read/ write are enabled. When the mode changes, the serial clock counter is reset.

Pins for connecting a system clock resonator. A 6-MHz crystal or ceramic resonator must be used. The accuracy of the frequency is as follows; Mode 0, 1: ±1.5%

Ground pin I/O pins connected to the IEBus bus

Main power supply pin for the IEBus bus driver/ receiver. When used, this pin must be tied to VDD.

Input pin used to select either 3- or 2-wire serial I/O mode. A high-level signal on this pin selects 3-wire serial I/O mode. A low-level signal on this pin selects 2-wire serial I/O mode.

Chip select pin. When this pin is driven low, the serial interface is enabled. When this pin is driven high, the SO pin becomes high-impedance, and the serial clock counter is reset.

I/O format

CMOS input CMOS input

(CMOS I/O)

CMOS output (none)

CMOS output

CMOS input

–

– –

–

CMOS input

Note

When reset

[for both hardware

and software] Input Input

High-impedance

Low level

Input

When reset by hardware (Oscillation stopped) XI = GND XO = High level When reset by software (Oscillation continued)

– High-impedance

–

Input

Note Parentheses indicate the state corresponding to two-wire serial I/O mode.

Data Sheet S14870EJ1V0DS00

PD72042

Pin No.

RESET

TEST

VDD

Input

–

I/O

Function

Serial reset signal input pin. A low input causes a reset. Whenever the power is turned on, a low-level signal must be applied to this pin. During normal operation, a high level is applied.

IC test pin. When used, this pin must be tied to the VDD pin directly.

Main power supply input pin

I/O format

CMOS input

–

When reset

[for both hardware

and software]

Input

–

Data Sheet S14870EJ1V0DS00

PD72042

2. IEBus OPERATION

2.1 OVERVIEW

PD72042 is a CMOS LSI device for the IEBus interface.

The The IEBus is designed to enable the data transmission between devices in a small-scale digital data transmission

system.

PD72042 is connected to a microcomputer built into a device. A serial interface (SCK, SO, and SI pins) is

The used for connection. The host controller (microcomputer) sets the commands and data needed for data transmission via this serial interface.

When data is transmitted, the host controller sets the data in the Then, signals are output on the BUS pins (BUS+, BUS–). When data is received from the BUS pins, the host controller can read it via the serial interface.

PD72042 via the serial interface.

Data Sheet S14870EJ1V0DS00

2.2 IEBus COMMUNICATION PROTOCOL

The IEBus is outlined below.

• Communication method: Half duplex asynchronous communication

• Multi-master method All units connected to the IEBus can transmit data to every other connected unit.

• Broadcast function (one-unit-to-multiple-units communication) Group broadcast : Broadcast to a specific group of units General broadcast : Broadcast to all units

• Two modes, each offering different transmission speeds, can be selected.

PD72042

Transmission speed

Mode 0 Approx. 3.9 Kbps 16 Mode 1 Approx. 17 Kbps 32

• Access control: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Bus mastership priority is as follows:

1 Broadcast takes priority over ordinary communication (one-unit-to-one-unit communication). 2 Units having lower master addresses have a higher priority.

• Communication scale Number of units : 50 max Cable length : 150 m max (when twisted-pair cable is used <resistance 0.1 Ω/m or less>) Load capacity : 7000 pF max <between BUS+ and BUS–> Terminating resistance : 120 Ω

Maximum number of bytes transmitted (bytes/frame)

Data Sheet S14870EJ1V0DS00

2.2.1 Bus Mastership Determination (Arbitration)

Before devices connected to the IEBus can control other devices, they must first acquire the bus. This operation

is called arbitration.

When more than one unit starts transmission at the same time, arbitration determines which of those units is allowed

to use the bus.

When arbitration results in only one device being granted bus mastership, the following bus mastership priority

conditions are used:

Remark Those devices that are defeated in arbitration can automatically enter retransmission mode. (For the

PD72042, the number of retransmissions can be set by specifying a value between 0 and 7 in the MCR

(1) Priority by communication type

Broadcast (one-unit-to-multiple-units communication) takes priority over ordinary communication (one-unit-toone-unit communication).

(2) Priority by master address

If the communication type is the same, the smallest master address value has the highest priority.

PD72042

Example Each master address consists of 12 bits. A unit having master address 000H has the highest priority,

while a unit having master address FFFH has the lowest priority.

2.2.2 Communication Mode

The IEBus supports two communication modes, each having a different transmission speed. Table 2-1 lists the transmission speed for each communication mode and the maximum number of bytes transmitted within one communication frame.

Table 2-1 Transmission Speed and Maximum Number of Transmission

Bytes in Each Communication Mode

Communication mode

0 16 Approx. 3.9 1 32 Approx. 17

Maximum number of transmission

bytes (bytes/frame)

Effective transmission speed

Note

(Kbps)

Note Effective transmission speed at which the maximum transfer rate is achieved

Caution Before devices connected to the IEBus can perform communication, an appropriate commun-

ication mode must be set. Note that if a master unit and an associated unit (slave unit) have different communication modes, they will not be able to communicate properly.

Data Sheet S14870EJ1V0DS00

PD72042

2.2.3 Communication Address

With the IEBus, each device is assigned a unique 12-bit communication address. The communication address

consists of the following parts:

High-order 4 bits : Group number (number identifying the group to which a device belongs) Low-order 8 bits : Unit number (number identifying a device in a group)

2.2.4 Broadcast

In ordinary communication, transmission and reception are performed between one master unit and one associated slave unit. Broadcast can also be done between one master unit and more than one slave unit. In this case master unit transmits data to an arbitrary number of slave units. In this case, the slave units do not return on acknowledge signal to the master unit.

Whether the communication to be performed is broadcast or ordinary communication is determined by the setting of the broadcast bit. (For details of the broadcast bit, see (1) 2 in Section 2.3.)

There are two types of broadcast.

(1) Group broadcast

Broadcast is performed to the devices in a particular group. These devices all have the same group number, as indicated by the high-order 4 bits of each communication address.

(2) General broadcast

Broadcast is performed to all devices, regardless of their group numbers. These two types of broadcast are distinguished by the slave address. (For details of the slave address, see (3) in Section 2.3.)

2.3 TRANSMISSION PROTOCOL

Fig. 2-1 shows the IEBus transmission signal format.

Communication data is transmitted as a sequence of signals called a communication frame. The transmission speed and the maximum amount of data that can be transmitted in one communication frame depend on the communication mode.

Data Sheet S14870EJ1V0DS00

Fig. 2-1 Transmission Signal Format

PD72042

Field name

Number of bits

Transmission

time

Mode 0

Mode 1

Header

Broad-

Start

cast

bit

Master

address field

12 1

Master

address

Slave

address field

12 1 1

P Slave

address

Approx. 7330

Approx. 2090

Control field

411

P A Control

bits

Data-length

field

811

Data-

length

P A Data

bits

P : Parity bit (1 bit) A : Acknowledge bit (1 bit)

When A = 0: ACK When A = 1: NAK

N : Number of data bytes

Remark For broadcast, the value of the acknowledge bit is ignored.

(1) Header

The header consists of a start bit and a broadcast bit. These are explained below.

Data field

811 811

P A Data

bits

Approx. 1590 × N

Approx. 410 × N

bits

1 Start bit

The start bit is a signal used to notify the other units of the beginning of data transmission. Before a unit starts data transmission, it outputs a low-level signal (start bit) for a specified duration, then outputs the broadcast bit. When the unit attempts to output the start bit, another unit may have already output the start bit. In such a case, the unit does not output the start bit, and instead waits for the other unit to stop outputting the start bit. Then, synchronized with the completion of start bit output by the other unit, the unit starts output of the broadcast bit. All units, except that unit which started the transmission, detect the start bit and become ready for reception.

2 Broadcast bit

The broadcast bit is used to distinguish between broadcast and ordinary communication. If the broadcast bit is 0, broadcast is indicated. If the broadcast bit is 1, ordinary communication is indicated. There are two types of broadcast: group broadcast and general broadcast. These types are distinguished by the slave address. (For details of the slave address, see (3).) For broadcast, more than one slave unit can exist as an associated communication station. Therefore, the acknowledge bits for the master address field and subsequent fields are not returned. When more than one unit starts sending a communication frame at the same time, broadcast takes precedence over ordinary communication and wins arbitration.

Data Sheet S14870EJ1V0DS00

PD72042

(2) Master address field

The master address field is used to transmit the local unit address (master address) to other units. The master address field consists of master address bits and a parity bit. A master address consists of 12 bits. It is output starting with the MSB. When more than one unit starts transmitting the same broadcast bit value at the same time, arbitration determination is performed by the master address field. Each time a unit transmits one bit of the master address field, the unit compares its output data with the data on the bus. If the comparison indicates that the master address output by the unit differs from the data on the bus, the unit determines that it has lost an arbitration. The unit stops transmission, and readies itself for reception. The IEBus is organized by wired AND. When arbitration is performed between units (arbitration masters), the unit having the smallest master address value wins the arbitration. After the 12-bit master address has been output, only one unit is finally determined as being the master unit, such that that unit remains in the transmission state.

Note

Next, the master unit outputs a parity bit proceeds to the slave address field.

Note Even parity is used. When the number of 1’s in the master address bits is odd, the parity bit is set to 1.

to post the master address to other units. Then, the master unit

(3) Slave address field

The slave address field is used to transmit the address (slave address) of a unit (slave unit) with which the master unit wants to communicate. The slave address field consists of slave address bits, a parity bit, and an acknowledge bit. A slave address consists of 12 bits. It is output starting with the MSB. After a 12-bit slave address has been transmitted, a parity bit is output to prevent the slave address from being received incorrectly. Then, the master unit attempts to detect the acknowledge signal from a slave unit to confirm that the slave unit exists on the bus. When the acknowledge signal is detected, the master unit outputs a control field. Note, however, that when performing broadcast, the master unit outputs the control field without attempting to detect the acknowledge bit. The slave unit outputs an acknowledge signal when the slave unit recognizes a match between the slave unit’s address and the slave address transmitted by the master unit match, and that both the master address and slave address have even parity. If the slave unit detects odd parity, it does not recognize the addresses as matching, so does not output an acknowledge signal. In this case, the master unit is placed in the standby (monitor) state, and communication terminates. For broadcast, the slave address is used to distinguish between group broadcast or general broadcast, as follows:

When the slave address is FFFH : General broadcast When the slave address is other than FFFH : Group broadcast

Remark For group broadcast, the number of a target group is indicated by the high-order 4 bits of the slave

address.

Data Sheet S14870EJ1V0DS00

(4) Control field

The control field indicates the type and direction of the next data field. The control field consists of control bits, a parity bit, and an acknowledge bit. The four control bits are output starting with the MSB. Following the control bits, a parity bit is output. If even parity is detected, and the function requested by the master unit can be performed by the slave unit, the slave unit outputs an acknowledge signal. Then, the slave unit proceeds to the data-length field. If the slave unit cannot perform the processing requested by the master unit, even when even parity is detected, or if odd parity is detected, the slave unit does not output an acknowledge signal, and it enters the standby (monitor) state again. After detecting the acknowledge signal, the master unit proceeds to the data-length field. If an acknowledge signal is not detected, the master unit enters the standby state, terminating communication. For broadcast, however, the master unit proceeds to the next data-length field without attempting to detect the acknowledge signal.

Table 2-3 lists the meanings of the control bits.

(5) Data-length field

The data-length field specifies the communication data length, in bytes. The data-length field consists of the data-length bits, a parity bit, and an acknowledge bit. The eight data-length bits are output starting with the MSB. The data-length bits indicate the communication data length, in bytes, as shown in Table 2-2.

PD72042

Table 2-2 Values of the Data-Length Bits and Their Meanings

Data-length bit (hexadecimal) Transmission data length, in bytes

01H 1 02H 2

:: ::

FFH 255

00H 256

Remark If the data length set in the data-length bits exceeds the maximum number of transmission bytes, the

latter varying with the communication mode, more than one frame is transmitted. In the second and subsequent frames, the data-length bits indicate the remaining communication data length, in bytes.

The operation performed for this field differs depending on whether master transmission (when bit 3 of the control

bits is 1) or master reception (when bit 3 of the control bits is 0) is performed.

1 Master transmission

The data-length bits and parity bit are output by the master unit. When the slave unit detects even parity, the slave unit outputs an acknowledge signal, then proceeds to the data field. For broadcast, however, the slave unit does not output an acknowledge signal. If the slave unit detects odd parity, the slave unit does not output an acknowledge signal, regarding the received data-length bits as being incorrect. Then, the slave unit enters the standby (monitor) state again. At this time, the master unit also enters the standby state again, and communication terminates.

Data Sheet S14870EJ1V0DS00

PD72042

2 Master reception

The data-length bits and parity bit are output by the slave unit. When the master unit detects even parity, the master unit outputs the acknowledge signal. If the master unit detects odd parity, the master unit does not output an acknowledge signal, regarding the received data-length bits as being incorrect. Then, the master unit enters the standby state again. At this time, the slave unit also enters the standby state again, and communication terminates.

(6) Data field

The data field is used for data transmission and reception to and from a slave unit. The master unit uses the data field to transmit data to the slave unit, or to receive data from the slave unit. The data field consists of data bits, a parity bit, and an acknowledge bit. The eight data bits are output, starting with the MSB. After the data bits have been output, the parity bit and acknowledge bit are output from the master unit and slave unit, respectively. Broadcast is performed only when the master unit transmits data. At this time, any acknowledge signal is ignored. The operations related to master transmission and master reception are explained below.

1 Master transmission

When the master unit performs a write to a slave unit, the master unit transmits the data bits and a parity bit to the slave unit. The slave unit receives the data bits and parity bit, then outputs an acknowledge signal if even parity is detected and the reception buffer is empty. If odd parity is detected, or if the reception buffer is not empty, the slave unit rejects the corresponding data, and does not output an acknowledge signal. If no acknowledge signal is received from the slave unit, the master unit transmits the same data again. The master unit repeats this operation until it receives an acknowledge signal from the slave unit, or until the data exceeds the maximum number of transmission bytes. When even parity is detected, and an acknowledge signal is received from the slave unit, the master unit transmits the subsequent data, if any, and provided the maximum number of transmission bytes is not reached. For broadcast, an acknowledge signal is not output by any slave unit. The master unit transfers data one byte at a time.

2 Master reception

When the master unit reads data from a slave unit, the master unit outputs a synchronization signal for each bit as it is read. The slave unit outputs data and a parity bit to the bus according to the synchronization signal output by the master unit. The master unit reads the data and parity bit output by the slave unit, and checks the parity. If the master unit detects odd parity, or if the reception buffer is not empty, the master unit rejects the data, and does not output an acknowledge signal. The master unit repeats the read operation for the same data provided the maximum allowable number of transmission bytes per communication frame has not been reached. If the master unit confirms even parity, and the reception buffer is empty, the master unit accepts the data, and returns an acknowledge signal to the slave unit. Then, the master unit reads the next data, provided the maximum allowable number of transmission bytes per frame has not been reached.

Data Sheet S14870EJ1V0DS00

(7) Parity bit

A parity bit is used to check for errors in the transmission data. A parity bit is added to the master address bits, slave address bits, control bits, data-length bits, and data bits. Even parity is used. If the number of 1’s in the data is odd, the parity bit is set to 1. If the number of 1’s in the data is even, the parity bit is set to 0.

(8) Acknowledge bit

In ordinary communication (one-unit-to-one-unit communication), an acknowledge bit is added in the following positions to confirm that data has been received correctly:

• At the end of the slave address field

• At the end of the control field

• At the end of the data-length field

• At the end of the data field

The acknowledge bit is defined as follows:

• 0: Indicates that transmission data has been recognized. (ACK)

• 1: Indicates that no transmission data has been recognized. (NAK)

PD72042

For broadcast, the acknowledge bit is ignored.

1 Acknowledge bit at the end of the slave address field

If any of the following is detected, the acknowledge bit at the end of the slave address field is set to NAK, and transmission is stopped:

• The parity of the master address bits or slave address bits is incorrect.

• A timing error occurred (bit format error).

• No slave unit is found.

2 Acknowledge bit at the end of the control field

If any of the following is detected, the acknowledge bit at the end of the control field is set to NAK, and transmission is stopped:

• The parity of the control bits is incorrect.

Note

• Although the slave reception buffer

• Although the slave transmission buffer

• For a locked unit, a unit other than the unit that specified the lock makes a request by using control bits indicating 3H, 6H, 7H, AH, BH, EH, or FH.

• Although no lock has been set, control bits indicating lock address read (4H) are set.

• A timing error occurred.

• An undefined control bit setting has been made.

is not empty, bit 3 of the control bits is 1 (write operation).

Note

is empty, the control bits indicate data read (3H, 7H).

Note See (1) in Section 2.4.

Data Sheet S14870EJ1V0DS00

PD72042

3 Acknowledge bit at the end of the data-length field

If any of the following is detected, the acknowledge bit at the end of the data-length field is set to NAK, and transmission is stopped:

• The parity of the data-length bits is incorrect.

• A timing error occurred.

4 Acknowledge bit at the end of the data field

If any of the following is detected, the acknowledge bit at the end of the data field is set to NAK, and transmission is stopped:

Note

• The parity of the data bits is incorrect

• A timing error occurred after the previous acknowledge bit.

• The reception buffer is full, such that no more data can be accepted

Note In this case, if the maximum allowable number of transmission bytes per frame has not yet been reached,

the transmitter retries transmission of the data field until the maximum number of transmission bytes is reached.

Note

2.4 TRANSMISSION DATA (CONTENTS OF THE DATA FIELD)

The contents of the data field are indicated by the control bits.

Data Sheet S14870EJ1V0DS00

Table 2-3 Meanings of the Control Bits

PD72042

Note 1

Bit 3

0H 0 0 0 0 Read slave status (SSR) 1H 0 0 0 1 Undefined 2H 0 0 1 0 Undefined 3H 0 0 1 1 Read data and locking 4H 0 1 0 0 Read lock address (low-order 8 bits) 5H 0 1 0 1 Read lock address (high-order 4 bits) 6H 0 1 1 0 Read slave status (SSR) and unlocking 7H 0 1 1 1 Read data 8H 1 0 0 0 Undefined 9H 1 0 0 1 Undefined AH 1 0 1 0 Write command and locking

BH 1 0 1 1 Write data and locking CH 1 1 0 0 Undefined DH 1 1 0 1 Undefined EH 1 1 1 0 Write command FH 1 1 1 1 Write data

Bit 2 Bit 1 Bit 0 Function

Note 2

Notes 1. The transfer direction of the data-length bits of the subsequent data-length field and data in the data

field changes according to the value of bit 3 (MSB). When bit 3 is 1: Transfer from the master unit to the slave unit When bit 3 is 0: Transfer from the slave unit to the master unit

2. The values of control bits 3H, 6H, AH, and BH specify locking and unlocking. When an undefined value, 1H, 2H, 8H, 9H, CH, or DH, is transmitted, no acknowledge signal is returned.

Once a unit has been locked by a master unit, the locked unit rejects the control bits received from other than the master unit that requested the lock, unless the value of the control bits is one of the values listed in Table 2-4. Then, the unit does not output the acknowledge bit.

Table 2-4 Control Field Acceptable to a Locked Slave Unit

Bit 3 Bit 2 Bit 1 Bit 0 Function 0H 0 0 0 0 Read slave status 4H 0 1 0 0 Read lock address (low-order 8 bits) 5H 0 1 0 1 Read lock address (high-order 4 bits)

(1) Reading the slave status (SSR) (control bits: 0H, 6H)

A master unit can read the slave status (0H, 6H) to determine why the slave unit did not return the acknowledge bit (ACK). The slave status is determined from the result of the communication last performed by the slave unit. All slave units can provide slave status information. Table 2-5 lists the slave status meanings.

Data Sheet S14870EJ1V0DS00

Fig. 2-2 Slave Status (SSR) Bit Format

PD72042

MSB

bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

Table 2-5 Slave Status Meanings

Bit Value Meaning

Note 1

Bit 0

Note 2

Bit 1

Bit 2 0 The unit is not locked.

Bit 3 0 Fixed at 0

Note 3

Bit 4

Bit 5 0 Fixed at 0 Bit 7 00 Mode 0 Bit 6 01 Mode 1

0 The slave transmission buffer is empty. 1 The slave transmission buffer is not empty. 0 The slave reception buffer is empty. 1 The slave reception buffer is not empty.

1 The unit is locked.

0 Slave transmission disabled 1 Slave transmission enabled

Indicates the highest mode supported by the

Note 4

unit

LSB

10 Reserved for future expansion 11

Notes 1. The slave transmission buffer is accessed during a data read operation (control bits: 3H, 7H).

For the µPD72042, this buffer corresponds to the TBF available when STRQ of the FLG register is set to 1.

2. The slave reception buffer is accessed during a data write operation (control bits: 8H, AH, BH, EH, FH).

For the

PD72042, this buffer corresponds to the RBF available when SLRE of the FLG register is set

to 1.

3. The value of bit 4 can be selected by using the UAR1 register.

4. Bits 7 and 6 are currently fixed to 10 in the hardware of the

PD72042.

(2) Data/command transfer (control bits: Read (3H, 7H), write (AH, BH, EH, FH))

When data read (3H, 7H) is set, the data in the data buffer of the slave unit is read into the master unit. When data write (BH, FH) or command write (AH, EH) is set, the data received by the slave unit is processed according to the operation specifications for the slave unit.

Remarks 1. The user can select data and commands as necessary according to the system.

2. 3H, AH, and BH may cause locking, depending on the communication conditions and status.

Data Sheet S14870EJ1V0DS00

(3) Reading a lock address (control bits: 4H, 5H)

When a lock address read operation (4H, 5H) is specified, the address (12 bits) of the master unit that issued the lock instruction is read in one-byte form, as shown below.

Fig. 2-3 Lock Address Format

MSB LSB

PD72042

Control bits : 4H

Control bits : 5H

(4) Locking and unlocking (control bits: Locking (3H, AH, BH), unlocking (6H))

The lock function is used to enable the transfer a message using more than one communication frame. When locked, a unit cannot receive data from other than the unit that requested the lock. Locking and unlocking are performed as follows:

1 Locking

The master unit can lock the slave unit by specifying the lock with the corresponding control bits (3H, AH, BH). In this case, when the transmission or reception of acknowledge bit 0 for the data-length field has been completed, but the communication frame is then terminated before transmission or reception of as many data bytes as are specified by the data-length bits is completed, the slave unit is locked. At this time, the bit indicating the lock status (bit 2) in the slave status byte is set to 1.

2 Unlocking

The master unit can unlock a locked slave unit when the control bits specify locking (3H, AH, or BH) or unlocking (6H). The slave unit is unlocked once as many data bytes as are specified by the data-length bits have been transmitted or received within one communication frame. At this time, the bit indicating the lock status (bit 2) in the slave status byte is reset to 0. For broadcast, locking or unlocking is not performed.

Low-order 8 bits

Undefined High-order 4 bits

Caution When a locked unit is to be unlocked by the unit itself, hardware reset or software reset must

be performed. (The lock status can be checked by referring to the contents of the LOR2 register.)

Data Sheet S14870EJ1V0DS00

2.5 BIT FORMAT

Fig. 2-4 illustrates the bits that constitute an IEBus communication frame.

Fig. 2-4 IEBus Bit Format (Concept)

Logic "1"

Logic "0"

PD72042

Preparation

period

Logic 1: The potential difference between the bus lines (the BUS+ and BUS- pins) is 20 mV or less (low level). Logic 0: The potential difference between the bus lines (the BUS+ and BUS- pins) is 120 mV or more (high level).

Synchronization

period

Data period

Preparation

period

Synchronization

period

Data period

Preparation period : First and subsequent low-level (logic 1) periods Synchronization period : Next high-level (logic 0) period Data period : Period in which a bit value is indicated (logic 1 = low level, logic 0 = high level)

The synchronization and data periods are almost equal in duration.

For the IEBus, synchronization is established for each bit. The specifications of the total time required for a bit and the duration of each period allotted within the bit vary depending on the type of the transmission bits, and whether the unit is a master or slave.

Data Sheet S14870EJ1V0DS00

3. MICROCOMPUTER INTERFACE

3.1 TRANSFER METHOD

Either of two microcomputer interface modes can be selected: three-wire serial I/O mode or two-wire serial I/O

mode.

Whether three-wire serial I/O mode or two-wire serial I/O mode is selected depends on the input level of the SEL

pin (pin 12). (See Section 3.3 for details.)

SEL ← 1: Three-wire serial I/O SEL ← 0: Two-wire serial I/O

(1) Three-wire serial I/O (SEL ← 1)

Three wires are used to read and write data. The three wires are the serial clock input (SCK), serial data input

Note 1

(SI

(a) Read operation

), and serial data output (SO

Data is output to the SO pin upon detecting the falling edge of the SCK pin.

Note 2

PD72042

(b) Write operation

Data is input via the SI pin upon detecting the rising edge of the SCK pin. At this time, 1 is output on the SO pin.

(2) Two-wire serial I/O (SEL ← 0)

Two wires are used to read and write data. The two wires are the serial clock input (SCK) and serial data I/O

Note 1

(SIO

(a) Read operation

(b) Write operation

Notes 1. The SI pin for three-wire serial I/O mode is also used as the SIO pin for two-wire serial I/O mode.

The SIO pin is placed in the output state, and data is output upon detecting the falling edge of the SCK pin.

The SIO pin is placed in the input state, and data is input upon detecting the rising edge of the SCK pin.

2. The impedance of the SO pin for three-wire serial I/O mode goes high in two-wire serial I/O mode. So, connect the SO pin to GND or V

DD.

Data Sheet S14870EJ1V0DS00

Table 3-1 I/O States of the SIO (SI) and SO Pins

PD72042

RESET CS SEL C/D SI (SIO) SO

Three-wire/two-wire Operating mode 0 ×××I Hi-Z – Reset state 11×× I Hi-Z – Chip nonselected state 1 0 1 1 I O* Three-wire Control mode

0 Data write mode

O Data read mode

0 1 I Hi-Z Two-wire Control mode

0 Data write mode

O Data read mode

State

I : Input state Hi-Z : High-impedance state O : Output state × : Don’t care O* : State in which 1 is output

3.2 DATA TRANSFER FORMAT

3.2.1 Three-Wire Data Transfer (SEL = 1)

(1) Control mode

When the C/D input is set high, control mode is set to control data transfer. Data transfer control involves the following processing. 1 Register address setting 2 Register read/write selection

C/D

SCK

SIO

A3 A2 A1 A0

×××

Remark After reset (RESET) cancellation, the state enabling writing to the register at address 0000B is set.

Caution In control mode, each data item is read every eighth clock pulse. (Data of less than eight clock

periods is ignored.)

Data Sheet S14870EJ1V0DS00

(2) Data read mode

When the C/D pin is set low after register read is selected in control mode, the data read mode is set. In data read mode, the data in a read register is read on the SO pin upon detecting the falling edge of the SCK pin.

C/D

SCK

PD72042

State

Serial clock counter

reset pointer

A3 A2 A1 A0 ×××

“1”

Control mode

(selection of register read)

D7 D6 D5 D4 D3 D2 D1 D0

Data read mode

Caution When the C/D pin is set high in data read mode, the serial clock counter is reset. Therefore, the

remaining bits of the byte cannot be read; at the next falling edge, read is performed starting from the next byte in the case of RBF, or from the first bit for other registers.

(3) Data write mode

When the C/D pin is set low after register write has been selected in control mode, data write mode is set. In data write mode, data for a write register is applied to the SI pin at the rising edge of the SCK pin.

C/D

SCK

A3 A2 A1 A0 ×××

D7 D6 D5 D4 D3 D2 D1 D0

State

Serial clock counter

reset pointer

“1”

Control mode

(selection of register write)

Data write mode

Caution Register overwrite is started immediately after the eighth clock rising edge. All registers other

than TBF are overwritten on the eighth clock rising edge. (Data of less than eight clock periods is ignored.)

Data Sheet S14870EJ1V0DS00

PD72042

3.2.2 Two-Wire Data Transfer (SEL = 0)

(1) Control mode

When the C/D input is set high, control mode is set to control data transfer. Data transfer control involves the following processing. 1 Register address setting 2 Register read/write selection

C/D

SCK

SIO

A3 A2 A1 A0

×××

Remark After reset (RESET) cancellation, the state enabling writing to the register at address 0000B is set.

Caution In control mode, each data item is read every eighth clock pulse. (Data of less than eight clock

periods is ignored.)

(2) Data read mode

C/D

SCK

SIO

State

Serial clock counter

reset pointer

Note

SIO pin input state

A3 A2 A1 A0 ×××

(selection of register read)

Control mode

D7 D6 D5 D4 D3 D2 D1 D0

Data read mode

SIO pin output state

Cautions 1. When the C/D pin is set high in data read mode, the serial clock counter is reset. Therefore,

the remaining bits of the byte cannot be read; at the next falling edge, a read operation is performed starting from the next byte in the case of RBF, or from the first bit for other registers.

2. The SIO pin is a CMOS I/O pin. So, be careful to avoid an output collision between the SIO pin and the microcomputer. Further, a pull-up resistor is required when N-ch open-drain output of the microcomputer is used. Note that if the last output level is low upon the termination of read mode, current will flow constantly.

Data Sheet S14870EJ1V0DS00

(3) Data write mode

C/D

SCK

PD72042

SIO

Serial clock counter

reset pointer

Note

State

SIO pin input state

A3 A2 A1 A0 ×××

Control mode

(selection of register write)

D7 D6 D5 D4 D3 D2 D1 D0

Date write mode

Caution Register overwrite is started immediately after the eighth clock rising edge. All registers other

than TBF are overwritten at the eighth clock rising edge. (Data of less than eight clock periods is ignored.)

Data Sheet S14870EJ1V0DS00

3.3 CONNECTION TO A MICROCOMPUTER

(1) Three-wire serial I/O

120 Ω

PD72042

(2) Two-wire serial I/O

120 Ω

5 V

6 MHz

5 V

6 MHz

V AV

TEST BUS+ BUS– XI XO GND

AV TEST

BUS+ BUS–

XI XO GND

PD72042

SEL

Note 1

SCK

Note 2

IRQ

RESET

IRQ

RESET

C/D

SCK

SEL

Note 1

C/D

SIO

Note 2

5 V

Low voltage detection circuit

5 V

Low voltage detection circuit

Microcomputer

Output port Output port SCK SO SI INT

75XL series 78K series

Microcomputer

Output port Output port SCK

Note 3

SIO

INT

75XL series 78K series

Notes 1. When only the µPD72042 is to be controlled from a microcomputer via a serial I/O interface, the CS pin

must be tied low (by connecting it to GND).

2. When an interrupt is detected by polling (in FLG register read), IRQ may be left open. When high-volume or high-speed data transfer is required, however, the system described above is recommended to ensure reliable data transfer.

3. Required when the microcomputer’s N-ch open-drain output is used. The SIO pin of the

PD72042 is

a CMOS I/O pin.

Data Sheet S14870EJ1V0DS00

3.4 STANDBY MODE SETTING AND CANCELLATION

Standby mode can be set by setting STREQ of the CTR register to 1. The XI pin for oscillation is tied to GND,

and the impedance of the XO pin goes high.

In standby mode (with the STM flag of the FLG register set to 1), only the following registers can be accessed:

Writable register : CTR (address 0000B) Readable register : FLG (address 0001B)

Standby mode can be cancelled by setting STREQ of the CTR register to 0.

Caution Do not read any data from internal registers via the serial I/O during the period from when a

microcomputer sets the STREQ flag to 1 to when the period is one-communication frame at maximum.

3.5 RESET MODE SETTING AND CANCELLATION

For hardware reset, the registers are initialized and standby mode is set. (During this period, oscillation is stopped.) For software reset, the registers are initialized, and operation is started.

PD72042 enters the standby mode. This

PD72042

Data Sheet S14870EJ1V0DS00

+ 64 hidden pages

NEC UPD72042GT Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual

FEATURES

ORDERING INFORMATION

PIN CONFIGURATION (TOP VIEW)

BLOCK DIAGRAM

1. PIN FUNCTIONS

1.1 PIN FUNCTIONS

2. IEBus OPERATION

2.1 OVERVIEW

2.2 IEBus COMMUNICATION PROTOCOL

2.2.1 Bus Mastership Determination (Arbitration)

2.2.2 Communication Mode

2.2.3 Communication Address

2.2.4 Broadcast

2.3 TRANSMISSION PROTOCOL

2.4 TRANSMISSION DATA (CONTENTS OF THE DATA FIELD)

2.5 BIT FORMAT

3. MICROCOMPUTER INTERFACE

3.1 TRANSFER METHOD

3.2 DATA TRANSFER FORMAT

3.2.1 Three-Wire Data Transfer (SEL = 1)

3.2.2 Two-Wire Data Transfer (SEL = 0)

3.3 CONNECTION TO A MICROCOMPUTER

3.4 STANDBY MODE SETTING AND CANCELLATION

3.5 RESET MODE SETTING AND CANCELLATION