Datasheet IS80C52-12PL, IS80C52-40WI, IS80C52-40W, IS80C52-40PQI, IS80C52-40PQ Datasheet (ISSI)

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IS80C52

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21

T2/P1.0

T2EX/P1.1

P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RST

RxD/P3.0

TxD/P3.1 INT0/P3.2 INT1/P3.3

T0/P3.4 T1/P3.5

WR/P3.6

RD/P3.7

XTAL2 XTAL1

GND

P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 EA ALE PSEN P2.7/A15 P2.6/A14 P2.5/A13 P2.4/A12 P2.3/A11 P2.2/A10 P2.1/A9 P2.0/A8

IS80C52

IS80C32

ISSI

CMOS SINGLE CHIP

NOVEMBER 1998

LOW VOLTAGE 8-BIT MICROCONTROLLER

GENERAL DESCRIPTION

FEATURES

• 80C51 based architecture

• 8K x 8 ROM (IS80C52 only)

• 256 x 8 RAM

• Three 16-bit Timer/Counters

• Full duplex serial channel

• Boolean processor

• Four 8-bit I/O ports, 32 I/O lines

• Memory addressing capability – 64K ROM and 64K RAM

• Program memory lock – Encrypted verify (32 bytes) – Lock bits (2)

• Power save modes: – Idle and power-down

• Eight interrupt sources

• Most instructions execute in 0.3 µs

• CMOS and TTL compatible

• Maximum speed: 40 MHz @ Vcc = 5V

• Industrial temperature available

• Packages available: – 40-pin DIP – 44-pin PLCC – 44-pin PQFP

ISSI reserves the right to make changes to its products at any time without notice in order to improve design and supply the best possible product. We assume no responsibility for any errors which may appear in this publication. © Copyright 1998, Integrated Silicon Solution, Inc.

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The ISSI IS80C52 and IS80C32 are high-performance microcontrollers fabricated using high-density CMOS technology. The CMOS IS80C52/32 is functionally compatible with the industry standard 8052/32 microcontrollers.

The IS80C52/32 is designed with 8K x 8 ROM (IS80C52 only); 256 x 8 RAM; 32 programmable I/O lines; a serial I/O port for either multiprocessor communications, I/O expansion or full duplex UART; three 16-bit timer/counters; an eight-source, two-priority-level, nested interrupt structure; and an on-chip oscillator and clock circuit. The IS80C52/32 can be expanded using standard TTL compatible memory.

Figure 1. IS80C52/32 Pin Configuration:

40-pin PDIP

IS80C52 IS80C32

INDEX

P1.4

P1.3

P1.2

P1.1/T2EX

P1.0/T2NCV

P0.0/AD0

P0.1/AD1

P0.2/AD2

P0.3/AD3

ISSI

P1.5 P1.6 P1.7 RST

RxD/P3.0

TxD/P3.1 INT0/P3.2 INT1/P3.3

T0/P3.4 T1/P3.5

4365 2144

7 8 9 10 11 12 13 14 15 16 17

18 19 20 21 22 23 24

XTAL2

RD/P3.7

WR/P3.6

TOP VIEW

GND

XTAL1

43 42 41 40

25 26 27 28

A8/P2.0

A9/P2.1

A10/P2.2

39 38 37 36 35 34 33 32 31 30 29

A11/P2.3

A12/P2.4

P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 EA NC ALE PSEN P2.7/A15 P2.6/A14 P2.5/A13

Figure 2. IS80C52/32 Pin Configuration: 44-pin PLCC

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IS80C52 IS80C32

ISSI

P1.5 P1.6 P1.7 RST

RxD/P3.0

TxD/P3.1 INT0/P3.2 INT1/P3.3

T0/P3.4 T1/P3.5

P1.4

P1.3

P1.2

P1.1/T2EX

P1.0/T2NCV

1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18

P0.0/AD0

37 36 35 3444 43 42 41 40 39

19 20 21 22

P0.1/AD1

P0.2/AD2

P0.3/AD3

33 32 31 30 29 29 27 26 25 24 23

P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 EA NC ALE PSEN P2.7/A15 P2.6/A14 P2.5/A13

XTAL2

RD/P3.7

WR/P3.6

Figure 3. IS80C52/32 Pin Configuration: 44-pin PQFP

XTAL1

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GND

A8/P2.0

A9/P2.1

A10/P2.2

A11/P2.3

A12/P2.4

IS80C52 IS80C32

ISSI

GND

RAM ADDR

P2.0-P2.7

DRIVERS

ADDRESS

DECODER

& 256

BYTES RAM

STACK

POINT

PCON SCON TMOD TCON

T2CON TH0 TL0 TH1

TL1 TH2 TL2 RCAP2H

RCAP2L SBUF IE IP

INTERRUPT

SERIAL PORT

AND TIMER BLOCK

LATCH

P0.0-P0.7

ACC

TMP2

DRIVERS

LATCH

ALU

TMP1

ADDRESS DECODER

8K ROM

2 LOCK BITS

32 BYTES

ENCRYPTION

INCREMENTER

PROGRAM

ADDRESS

PROGRAM

COUNTER

PSEN

ALE

RST

TIMING

AND

CONTROL

OSCILLATOR

INSTRUCTION

XTAL2XTAL1

PSW

LATCH

DRIVERS

P3.0-P3.7

LATCH

DRIVERS

P1.0-P1.7

Figure 4. IS80C52/32 Block Diagram

BUFFER

DPTR

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IS80C52 IS80C32

Table 1. Detailed Pin Description Symbol PDIP PLCC PQFP I/O Name and Function

ALE 30 33 27 I/O Address Latch Enable: Output pulse for latching the low byte

of the address during an address to the external memory. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency, and can be used for external timing or clocking. Note that one ALE pulse is skipped during each access to external data memory.

P0.0-P0.7 39-32 43-36 37-30 I/O Port 0: Port 0 is an 8-bit open-drain, bidirectional I/O port. Port

31 35 29 I External Access enable: EA must be externally held low to

enable the device to fetch code from external program memory locations 0000H to FFFFH. If EA is held high, the device executes from internal program memory unless the program counter contains an address greater than 0FFFH.

0 pins that have 1s written to them float and can be used as high-impedance inputs. Port 0 is also the multiplexed loworder address and data bus during accesses to external program and data memory. In this application, it uses strong internal pullups when emitting 1s.

ISSI

P1.0-P1.7 1-8 2-9 40-44 I/O Port 1: Port 1 is an 8-bit bidirectional I/O port with internal

1-3 pullups. Port 1 pins that have 1s written to them are pulled high

by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally pulled low will source current because of the internal pullups. (See DC Characteristics: IIL). The Port 1 output buffers can sink/source four TTL inputs.

Port 1 also receives the low-order address byte during ROM verification.

1240IT2(P1.0): Timer/Counter 2 external count input. 2341IT2EX(P1.1): Timer/Counter 2 trigger input.

P2.0-P2.7 21-28 24-31 18-25 I/O Port 2: Port 2 is an 8-bit bidirectional I/O port with internal

pullups. Port 2 pins that have 1s written to them are pulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally pulled low will source current because of the internal pullups. (See DC Characteristics: IIL). Port 2 emits the high order address byte during fetches from external program memory and during accesses to external data memory that used 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ Ri [i = 0, 1]), Port 2 emits the contents of the P2 Special Function Register.

Port 2 also receives the high-order bits and some control signals during ROM verification.

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IS80C52 IS80C32

ISSI

Table 1. Detailed Pin Description Symbol PDIP PLCC PQFP I/O Name and Function

P3.0-P3.7 10-17 11, 13-19 5, 7-13 I/O Port 3: Port 3 is an 8-bit bidirectional I/O port with internal

10 11 5 I RxD (P3.0): Serial input port. 11 13 7 O TxD (P3.1): Serial output port. 12 14 8 I 13 15 9 I 14 16 10 I T0 (P3.4): Timer 0 external input. 15 17 11 I T1 (P3.5): Timer 1 external input. 16 18 12 O 17 19 13 O

PSEN

29 32 26 O Program Store Enable: The read strobe to external program

(continued)

pullups. Port 3 pins that have 1s written to them are pulled high by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally pulled low will source current because of the internal pullups. (See DC Characteristics: IIL).

Port 3 also serves the special features of the IS80C51/31, as listed below:

INT0INT0

INT0

(P3.2): External interrupt 0.

INT0INT0 INT1INT1

INT1

(P3.3): External interrupt 1.

INT1INT1

WRWR

(P3.6): External data memory write strobe.

WRWR RDRD

(P3.7): External data memory read strobe.

RDRD

memory. When the device is executing code from the external program memory, cycle except that two each access to external data memory. during fetches from internal program memory.

PSEN

is activated twice each machine

PSEN

activations are skipped during

PSEN

is not activated

RST 9 10 4 I Reset: A high on this pin for two machine cycles while the

oscillator is running, resets the device. An internal MOS resistor to GND permits a power-on reset using only an external capacitor connected to Vcc.

XTAL 1 19 21 15 I Crystal 1: Input to the inverting oscillator amplifier and

input to the internal clock generator circuits. XTAL 2 18 20 14 O Crystal 2: Output from the inverting oscillator amplifier. GND 20 22 16 I Ground: 0V reference. Vcc 40 44 38 I Power Supply: This is the power supply voltage for operation.

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IS80C52 IS80C32

OPERATING DESCRIPTION

ISSI

The detail description of the IS80C52/32 included in this description are:

•Memory Map and Registers

•Timer/Counters

•Serial Interface

•Interrupt System

•Other Information

MEMORY MAP AND REGISTERS Memory

The IS80C52/32 has separate address spaces for program and data memory. The program and data memory can be up to 64K bytes long. The lower 8K program memory can reside on-chip. (IS80C52 only) Figure 5 shows a map of the IS80C52/32 program and data memory.

The IS80C52/32 has 256 bytes of on-chip RAM, plus numbers of special function registers. The lower 128 bytes can be accessed either by direct addressing or by indirect addressing. The upper 128 bytes can be accessed by

indirect addressing only. Figure 6 shows internal data memory organization and SFR Memory Map.

The lower 128 bytes of RAM can be divided into three segments as listed below and shown in Figure 7.

locations 00H through 1FH (32 bytes). The device after reset defaults to register bank 0. To use the other register banks, the user must select them in software. Each register bank contains eight 1-byte registers R0-R7. Reset initializes the stack point to location 07H, and is incremented once to start from 08H, which is the first register of the second register bank.

Bit Addressable Area:

16 bytes have been assigned for this segment 20H-2FH. Each one of the 128 bits of this segment can be directly addressed (0-7FH). Each of the 16 bytes in this segment can also be addressed as a byte.

Scratch Pad Area:

30H-7FH are available to the user as data RAM. However, if the data pointer has been initialized to this area, enough bytes should be left aside to prevent SP data destruction.

FFFFH:

64K

EA = 0

External

PSEN

Program Memory

(Read Only)

1FFFH:

0000

EA = 1

Internal

(IS80C52

Only)

FFH:

External

Data Memory

(Read/Write)

FFFFH:

Internal

0000

Figure 5. IS80C52/32 Program and Data Memory Structure

RD WR

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IS80C52 IS80C32

SPECIAL FUNCTION REGISTERS

ISSI

The Special Function Registers (SFR's) are located in upper 128 Bytes direct addressing area. The SFR Memory Map in Figure 6 shows that.

Not all of the addresses are occupied. Unoccupied addresses are not implemented on the chip. Read accesses to these addresses in general return random data, and write accesses have no effect.

User software should not write 1s to these unimplemented locations, since they may be used in future microcontrollers to invoke new features. In that case, the reset or inactive values of the new bits will always be 0, and their active values will be 1.

The functions of the SFRs are outlined in the following sections, and detailed in Table 2.

Upper

128

Lower

128

FFH

80H

7FH

Accessible by Indirect

Addressing

Only

Accessible

by Direct

and Indirect

Addressing

Accessible

by Direct

Addressing

Special

Function

Registers

FFH

80H

Ports, Status and Control Bits, Timer, Registers, Stack Pointer, Accumulator (Etc.)

Accumulator (ACC)

ACC is the Accumulator register. The mnemonics for Accumulator-specific instructions, however, refer to the Accumulator simply as A.

B Register (B)

The B register is used during multiply and divide operations. For other instructions it can be treated as another scratch pad register.

Program Status Word (PSW). The PSW register contains program status information.

F0 E8

ACC

E0 D8

PSW

T2CON

C8 C0 B8 B0 A8 A0 98 90 88 80

Addressable

SCON

TCON

Bit

SBUF

TMOD

RCAP2L

TL0 DPL

RCAP2H

TL1

DPH

TL2

TH0

TH2

TH1

PCON

FF F7 EF E7 DF D7 CF C7 BF B7 AF A7 9F 97 8F 87

Figure 6. Internal Data Memory and SFR Memory Map

8 BYTES

78 70 68 60 58 50 48 40 38 30 28

0 ...

20 18 10 08 00

BANK3

BANK2 BANK 1 BANK 0

...7F

7F 77 6F 67 5F 57 4F 47 3F 37 2F

ADDRESSABLE

27 1F 17

0F 07

SCRATCH

PAD

AREA

BIT

SEGMENT

BANKS

Figure 7. Lower 128 Bytes of Internal RAM

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IS80C52 IS80C32

SPECIAL FUNCTION REGISTERS

(continued)

Stack Pointer (SP)

The Stack Pointer Register is eight bits wide. It is incremented before data is stored during PUSH and CALL executions. While the stack may reside anywhere in on-chip RAM, the Stack Pointer is initialized to 07H after a reset. This causes the stack to begin at location 08H.

Data Pointer (DPTR)

The Data Pointer consists of a high byte (DPH) and a low byte (DPL). Its function is to hold a 16-bit address. It may be manipulated as a 16-bit register or as two independent 8-bit registers.

Ports 0 To 3

P0, P1, P2, and P3 are the SFR latches of Ports 0, 1, 2, and 3, respectively.

ISSI

initiates the transmission.) When data is moved from SBUF, it comes from the receive buffer.

Timer Registers

Register pairs (TH0, TL0), (TH1, TL1), and (TH2, TL2) are the 16-bit Counter registers for Timer/Counters 0, 1, and 2, respectively.

Capture Registers

The register pair (RCAP2H, RCAP2L) are the Capture registers for the Timer 2 Capture Mode. In this mode, in response to a transition at the IS80C52/32's T2EX pin, TH2 and TL2 are copied into RCAP2H and RCAP2L. Timer 2 also has a 16-bit auto-reload mode, and RCAP2H and RCAP2L hold the reload value for this mode.

Serial Data Buffer (SBUF)

The Serial Data Buffer is actually two separate registers, a transmit buffer and a receive buffer register. When data is moved to SBUF, it goes to the transmit buffer, where it is held for serial transmission. (Moving a byte to SBUF

Control Registers

Special Function Registers IP, IE, TMOD, TCON, T2CON, SCON, and PCON contain control and status bits for the interrupt system, the Timer/Counters, and the serial port. They are described in later sections of this chapter.

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IS80C52 IS80C32

Table 2: Special Function Register

Symbol Description Direct Address Bit Address, Symbol, or Alternative Port Function Reset Value

(1)

ACC

(1)

B DPH Data pointer (DPTR) high 83H 00H DPL Data pointer (DPTR) low 82H 00H

(1)

PCON Power control 87H SMOD — — — GF1 GF0 PD IDL 0XXX0000B

(1)

PSW SBUF Serial data buffer 99H XXXXXXXXB

(1)

SCON SP Stack pointer 81H 07H

(1)

TCON TMOD Timer mode 89H GATE C/

T2CON

(1,2)

TH0 Timer high 0 8CH 00H TH1 Timer high 1 8DH 00H

(2)

TH2 TL0 Timer low 0 8AH 00H TL1 Timer low 1 8BH 00H RCAP2H RCAP2L

(2)

TL2

Notes:

1. Denotes bit addressable.

2. SFRs are added to the 80C51 SFRs.

Accumulator E0H E7 E6 E5 E4 E3 E2 E1 E0 00H

B register F0H F7 F6 F5 F4 F3 F2 F1 F0 00H

AF AE AD AC AB AA A9 A8

Interrupt enable A8H EA — ET2 ES ET1 EX1 ET0 EX0 0X000000B

BF BE BD BC BB BA B9 B8

Interrupt priority B8H — — PT2 PS PT1 PX1 PT0 PX0 XX000000B

87 86 85 84 83 82 81 80

Port 0 80H P0.7 P0.6 P0.5 P0.4 P0.3 P0.2 P0.1 P0.0 FFH

AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0

97 96 95 94 93 92 91 90

Port 1 90H P1.7 P1.6 P1.5 P1.4 P1.3 P1.2 P1.1 P1.0 FFH

—— ————T2EX T2

A7 A6 A5 A4 A3 A2 A1 A0

Port 2 A0H P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0 FFH

AD15 AD14 AD13 AD12 AD11 AD10 AD9 AD8

B7 B6 B5 B4 B3 B2 B1 B0

Port 3 B0H P3.7 P3.6 P3.5 P3.4 P3.3 P3.2 P3.1 P3.0 FFH

RD WR

T1 T0

INT1 INT0

TXD RXD

D7 D6 D5 D4 D3 D2 D1 D0

Program status word D0H CY AC F0 RS1 RS0 OV — P 00H

9F 9E 9D 9C 9B 9A 99 98

Serial controller 98H SM0 SM1 SM2 REN TB8 RB8 TI RI 00H

8F 8E 8D 8C 8B 8A 89 88

Timer control 88H TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 00H

M1 M0 GATE C/TM1 M0 00H

CF CE CD CC CB CA C9 C8

Timer/Counter 2 C8H TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2CP/

RL2

Timer high 2 CDH 00H

(2)

Capture high CAH 00H

(2)

Capture low CBH 00H

Timer low 2 CCH 00H

ISSI

00H

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ISSI

The detail description of each bit is as follows:

PSW:

Program Status Word. Bit Addressable.

76543210 CY AC F0 RS1 RS0 OV — P

CY PSW.7 Carry flag. AC PSW.6 Auxiliary carry flag. F0 PSW.5 Flag 0 available to the user for

general purpose. RS1 PSW.4 Register bank selector bit 1. RS0 PSW.3 Register bank selector bit 0.

(1) (1)

OV PSW.2 Overflow flag. — PSW.1 Usable as a general purpose flag P PSW.0 Parity flag. Set/Clear by hardware each

instruction cycle to indicate an odd/even

number of “1” bits in the accumulator.

Note:

1. The value presented by RS0 and RS1 selects the corresponding register bank.

RS1 RS0 Register Bank Address

0 0 0 00H-07H 0 1 1 08H-0FH 1 0 2 10H-17H 1 1 3 18H-1FH

PCON:

Power Control Register. Not Bit Addressable.

76543210 SMOD — — — GF1 GF0 PD IDL

SMOD Double baud rate bit. If Timer 1 is used to generate

baud rate and SMOD=1, the baud rate is doubled

when the serial port is used in modes 1, 2, or 3. — Not implemented, reserve for future use. — Not implemented, reserve for future use. — Not implemented, reserve for future use. GF1 General purpose flag bit. GF0 General purpose flag bit. PD Power-down bit. Setting this bit activates power-

down operation in the IS80C52/32. IDL Idle mode bit. Setting this bit activates idle mode

operation in the IS80C52/32. If 1s are written to

PD and IDL at the same time, PD takes

precedence.

Note:

1. User software should not write 1s to reserved bits. These bits

may be used in future products to invoke new features.

(1) (1) (1)

IE:

Interrupt Enable Register. Bit Addressable.

76543210 EA — ET2 ES ET1 EX1 ET0 EX0

EA IE.7 Disable all interrupts. If EA=0, no

interrupt will be acknowledged. If EA=1, each interrupt source is individually enabled or disabled by setting or clearing its enable bit.

— IE.6 Not implemented, reserve for future

ET2 IE.5 Enables or disables timer 2 overflow

ES IE.4 Enable or disable the serial port

ET1 IE.3 Enable or disable the timer 1 overflow

EX1 IE.2 Enable or disable external interrupt 1. ET0 IE.1 Enable or disable the timer 0 overflow

EX0 IE.0 Enable or disable external interrupt 0.

Note:

To use any of the interrupts in the 80C51 Family, the following three steps must be taken:

1. Set the EA (enable all) bit in the IE register to 1.

2. Set the coresponding individual interrupt enable bit in the IE register to 1.

3. Begin the interrupt service routine at the corresponding Vector Address of that interrupt (see below).

Interrupt Source Vector Address

IE0 0003H

TF0 000BH

IE1 0013H

TF1 001BH

RI & TI 0023H

TF2 and EXF2 002BH

4. In addition, for external interrupts, pins INT0 and INT1 (P3.2 and P3.3) must be set to 1, and depending on whether the interrupt is to be level or transition activated, bits IT0 or IT1 in the TCON register may need to be set to 0 or 1. ITX = 0 level activated (X = 0, 1) ITX = 1 transition activated

5. User software should not write 1s to reserved bits. These bits may be used in future products to invoke new features.

(5)

use.

interrupt.

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ISSI

IP:

Interrupt Priority Register. Bit Addressable.

76543210 — — PT2 PS PT1 PX1 PT0 PX0

— IP.7 Not implemented, reserve for future use — IP.6 Not implemented, reserve for future use PT2 IP.5 Defines Timer 2 interrupt priority level PS IP.4 Defines Serial Port interrupt priority level PT1 IP.3 Defines Timer 1 interrupt priority level PX1 IP.2 Defines External Interrupt 1 priority level PT0 IP.1 Defines Timer 0 interrupt priority level PX0 IP.0 Defines External Interrupt 0 priority level

Notes:

1. In order to assign higher priority to an interrupt the coresponding bit in the IP register must be set to 1. While an interrupt service is in progress, it cannot be interrupted by a lower or same level interrupt.

2. Priority within level is only to resolve simultaneous requests of the same priority level. From high to low, interrupt sources are listed below: IE0 TF0 IE1 TF1 RI or TI TF2 or EXF2 User software should not write 1s to reserved bits. These bits

3. may be used in future products to invoke new features.

(3)

TCON:

Timer/Counter Control Register. Bit Addressable

76543210 TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0

TF1 TCON.7 Timer 1 overflow flag. Set by hardware

when the Timer/Counter 1 overflows. Cleared by hardware as processor vectors to the interrupt service routine.

TR1 TCON.6 Timer 1 run control bit. Set/Cleared by

software to turn Timer/Counter 1 ON/ OFF.

TF0 TCON.5 Timer 0 overflow flag. Set by hardware

when the Timer/Counter 0 overflows. Cleared by hardware as processor vectors to the interrupt service routine.

TR0 TCON.4 Timer 0 run control bit. Set/Cleared by

software to turn Timer/Counter 0 ON/ OFF.

IE1 TCON.3 External Interrupt 1 edge flag. Set by

hardware when the External Interrupt edge is detected. Cleared by hardware when interrupt is processed.

IT1 TCON.2 Interrupt 1 type control bit. Set/Cleared

by software specify falling edge/low level triggered External Interrupt.

IE0 TCON.1 External Interrupt 0 edge flag. Set by

hardware when the External Interrupt edge is detected. Cleared by hardware when interrupt is processed.

IT0 TCON.0 Interrupt 0 type control bit. Set/Cleared

by software specify falling edge/low level triggered External Interrupt.

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ISSI

TMOD:

Timer/Counter Mode Control Register. Not Bit Addressable.

Timer 1 Timer 0

GATE C/

M1 M0 GATE C/

GATE When TRx (in TCON) is set and GATE=1, TIMER/

COUNTERx will run only while INTx pin is high (hardware control). When GATE=0, TIMER/ COUNTERx will run only while TRx=1 (software control).

Timer or Counter selector. Cleared for Timer

operation (input from internal system clock). Set

for Counter operation (input from Tx input pin). M1 Mode selector bit. M0 Mode selector bit.

Note 1:

M1 M0 Operating mode

0 0 Mode 0. (13-bit Timer) 0 1 Mode 1. (16-bit Timer/Counter) 1 0 Mode 2. (8-bit auto-load Timer/Counter) 1 1 Mode 3. (Splits Timer 0 into TL0 and

TH0. TL0 is an 8-bit Timer/Counter controller by the standard Timer 0 control bits. TH0 is an 8-bit Timer and is controlled by Timer 1 control bits.)

1 1 Mode 3. (Timer/Counter 1 stopped).

(1)

M1 M0

SCON:

Serial Port Control Register. Bit Addressable.

76543210 SM0 SM1 SM2 REN TB8 RB8 TI RI

SM0 SCON.7 Serial port mode specifier. SM1 SCON.6 Serial port mode specifier. SM2 SCON.5 Enable the multiprocessor com-

munication feature in mode 2 and 3. In mode 2 or 3, if SM2 is set to 1 then RI will not be activated if the received 9th data bit (RB8) is 0. In mode 1, if SM2=1 then RI will not be activated if valid stop bit was not received. In mode 0, SM2 should be 0.

REN SCON.4 Set/Cleared by software to Enable/

Disable reception.

TB8 SCON.3 The 9th bit that will be transmitted in

mode 2 and 3. Set/Cleared by software.

RB8 SCON.2 In modes 2 and 3, RB8 is the 9th data

bit that was received. In mode 1, if SM2=0, RB8 is the stop bit that was received. In mode 0, RB8 is not used.

TI SCON.1 Transmit interrupt flag. Set by

hardware at the end of the 8th bit time in mode 0, or at the beginning of the stop bit in the other modes. Must be cleared by software.

RI SCON.0 Receive interrupt flag. Set by hardware

at the end of the 8th bit time in mode 0, or halfway through the stop bit time in the other modes (except see SM2). Must be cleared by software.

Note:

(1)

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SM0 SM1 MODE Description Baud rate

0 0 0 Shift register Fosc/12 0 1 1 8-bit UART Variable 1 0 2 9-bit UART Fosc/64 or

Fosc/32

1 1 3 9-bit UART Variable

IS80C52 IS80C32

T2CON:

Timer/Counter 2 Control Register. Bit Addressable.

76543210

T2T2

TF2 EXF2 RCLK TCLK EXEN2 TR2 C/

TF2 T2CON.7 Timer 2 overflow flag set by hardware

and cleared by software. TF2 cannot be set when either RCLK = 1 or TCLK = 1.

EXF2 T2CON.6 Timer 2 external flag set when either a

capture or reload is caused by a negative transition on T2EX, and EXEN2 = 1. When Timer 2 interrupt is enabled, EXF2 = 1 causes the CPU to vector to the Timer 2 interrupt routine. EXF2 must be cleared by software.

RCLK T2CON.5 Receive clock flag. When set, causes

the Serial Port to use Timer 2 overflow pulses for its receive clock in modes 1 and 3. RCLK = 0 causes Timer 1 overflow to be used for the receive clock.

TLCK T2CON.4 Transmit clock flag. When set, causes

the Serial Port to use Timer 2 overflow pulses for its transmit clock in modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock.

EXEN2 T2CON.3

Timer 2 external enable flag. When set, allows a capture or reload to occur as a result of negative transition on T2EX if Timer 2 is not being used to clock the Serial Port, EXEN2 = 0 causes Timer 2 to ignore events at T2EX.

TR2 T2CON.2 Software START/STOP control for

Timer 2. A logic 1 starts the Timer.

C/T2 T2CON.1 Timer or Counter select. 0 = Internal

Timer. 1 = External Event Counter (triggered by falling edge).

CP/RL2 T2CON.0

Capture/Reload flag. When set, captures occur on negative transitions at T2EX if EXEN2 = 1. When cleared, auto-reloads occur either with Timer 2 overflows or negative transitions at T2EX when EXEN2 = 1. When either RCLK = 1 or TCLK = 1, this bit is ignored and the Timer is forced to auto-reload on Timer 2 overflow.

T2T2

CP/

RL2RL2

RL2

RL2RL2

ISSI

Notes:

1. Timer 2 Operating Modes

RCLK + TCLKCP/

0 0 1 16-Bit Auto-Reload 0 1 1 16-Bit Capture 1 X 1 Baud Rate Generator

X X 0 (Off)

2. User software should not write 1s to reserved bits. These bits may be used in future products to invoke new features.

RL2RL2

RL2

TR2 MODE

RL2RL2

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TIMER/COUNTERS

The IS80C52/32 has three 16-bit Timer/Counter registers: Timer 0, Timer 1, and in addition Timer 2. All three can be configured to operate either as Timers or event Counters.

As a Timer, the register is incremented every machine cycle. Thus, the register counts machine cycles. Since a machine cycle consists of 12 oscillator periods, the count rate is 1/12 of the oscillator frequency.

As a Counter, the register is incremented in response to a 1-to-0 transition at its corresponding external input pin, T0, T1, and T2. The external input is sampled during S5P2 of every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the count is incremented. The new count value appears in the register during S3P1 of the cycle following the one in which the transition was detected. Since two machine cycles (24 oscillator periods) are required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency. There are no restrictions on the duty cycle of the external input signal, but it should be held for at least one full machine cycle to ensure that a given level is sampled at least once before it changes.

In addition to the Timer or Counter functions, Timer 0 and Timer 1 have four operating modes: (13-bit timer, 16-bit timer, 8-bit auto-reload, split timer). Timer 2 in the IS80C52/ 32 has three modes of operation: Capture, Auto-Reoload, and Baud Rate Generator.

Timer 0 and Timer 1

Timer/Counters 0 and 1 are present in both the IS80C51/ 31 and IS80C52/32. The Timer or Counter function is selected by control bits C/T in the Special Function Regiser TMOD. These two Timer/Counters have four operating modes, which are selected by bit pairs (M1, M0) in TMOD. Modes 0, 1, and 2 are the same for both Timer/ Counters, but Mode 3 is different. The four modes are described in the following sections.

Mode 0:

Both Timers in Mode 0 are 8-bit Counters with a divide-by32 prescaler. Figure 8 shows the Mode 0 operation as it applies to Timer 1.

In this mode, the Timer register is configured as a 13-bit register. As the count rolls over from all 1s to all 0s, it sets the Timer interrupt flag TF1. The counted input is enabled to the Timer when TR1 = 1 and either GATE = 0 or = 1. Setting GATE = 1 allows the Timer to be controlled by external input

INT1

, to facilitate pulse width measurements. TR1 is a control bit in the Special Function Register TCON. Gate is in TMOD.

The 13-bit register consists of all eight bits of TH1 and the lower five bits of TL1. The upper three bits of TL1 are indeterminate and should be ignored. Setting the run flag (TR1) does not clear the registers.

Mode 0 operation is the same for Timer 0 as for Timer 1, except that TR0, TF0 and

INT0

replace the corresponding Timer 1 signals in Figure 8. There are two different GATE bits, one for Timer 1 (TMOD.7) and one for Timer 0 (TMOD.3).

INT1

OSC

(XTAL2)

OSC

S1 S2 S3

DIVIDE 12

T1 PIN

GATE

INT1 PIN

ONE MACHINE

CYCLE

S4 S5 S6 S1 S2 S3 S4 S5 S6 S1

P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1P2 P1P2P1P2 P1P2P1 P2

C/T = 0

C/T = 1

TR1

CONTROL

TL1

(5 BITS)

ONE MACHINE

CYCLE

TH1

(8 BITS)

Figure 8. Timer/Counter 1 Mode 0: 13-Bit Counter

TIMER

CLOCK

TL1

(8 BITS)

TH1

(8 BITS)

Figure 9. Timer/Counter 1 Mode 1: 16-Bit Counter

TF1

OVERFLOW

FLAG

INTERRUPT

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Mode 1:

Mode 1 is the same as Mode 0, except that the Timer register is run with all 16 bits. The clock is applied to the combined high and low timer registers (TL1/TH1). As clock pulses are received, the timer counts up: 0000H, 0001H, 0002H, etc. An overflow occurs on the FFFFH-to0000H overflow flag. The timer continues to count. The overflow flag is the TF1 bit in TCON that is read or written by software (see Figure 9).

Mode 2:

Mode 2 configures the Timer register as an 8-bit Counter (TL1) with automatic reload, as shown in Figure 10. Overflow from TL1 not only sets TF1, but also reloads TL1 with the contents of TH1, which is preset by software. The reload leaves the TH1 unchanged. Mode 2 operation is the same for Timer/Counter 0.

OSC

DIVIDE 12

T1 PIN

C/T = 0

C/T = 1

TR1

Mode 3:

Timer 1 in Mode 3 simply holds its count. The effect is the same as setting TR1 = 0. Timer 0 in Mode 3 establishes TL0 and TH0 as two separate counters. The logic for Mode 3 on Timer 0 is shown in Figure 10. TL0 uses the Timer 0 control bits: C/T, GATE, TR0, INT0, and TF0. TH0 is locked into a timer function (counting machine cycles) and over the use of TR1 and TF1 from Timer 1. Thus, TH0 now controls the Timer 1 interrupt.

Mode 3 is for applications requiring an extra 8-bit timer or counter. With Timer 0 in Mode 3, the IS80C51/31 can appear to have three Timer/Counters, and an IS80C52/32 can appear to have four. When Timer 0 is in Mode 3, Timer 1 can be turned on and off by switching it out of and into its own Mode 3. In this case, Timer 1 can still be used by the serial port as a baud rate generator or in any application not requiring an interrupt.

CONTROL

TL1

(8 BITS)

TF1

RELOAD

INTERRUPT

OSC

GATE

INT0 PIN

TH1

(8 BITS)

Figure 10. Timer/Counter 1 Mode 2: 8-Bit Auto-Reload

DIVIDE 12 1/12F OSC

1/12F OSC

T0 PIN

GATE

INT0 PIN

1/12F OSC

TR0

TR1

C/T = 0

C/T = 1

CONTROL

TL0

(8 BITS)

TH0

(8 BITS)

Figure 11. Timer/Counter 0 Mode 3: Two 8-Bit Counters

TF0

TF1

INTERRUPT

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Timer 2

Timer 2 is a 16-bit Timer/Counter present only in the IS80C52/32. This is a powerful addition to the other two just discussed. Five extra special function registers are added to accommodate Timer 2 which are: the timer registers, TL2 and TH2, the timer control register, T2CON, and the capture registers, RCAP2L and RCAP2H. Like Timers 0 and 1, it can operate either as a timer or as an event counter, depending on the value of bit C/T2 in the Special Function Register T2CON. Timer 2 has three operating modes: capture, auto-reload, and baud rate generator, which are selected by RCLK, TCLK, CP/RL2 and TR2.

In the Capture Mode, the EXEN2 bit in T2CON selects two options. If EXEN2 = 0, then Timer 2 is a 16-bit timer or counter whose overflow sets bit TF2, the Timer 2 overflow bit, which can be used to generate an interrupt. If EXEN2 = 1, then Timer 2 performs the same way, but a 1-to-0 transition at external input T2EX also causes the current value in the Timer 2 registers, TL2 and TH2, to be

captured into the RCAP2L and RCAP2H registers, respectively. In addition, the transition at T2EX sets the EXF2 bit in T2CON, and EXF2, like TF2, can generate an interrupt.

The Capture Mode is illustrated in Figure 12. In the auto-reload mode, the EXEN2 bit in T2CON also

selects two options. If EXEN2 = 0, then when Timer 2 rolls over it sets TF2 and also reloads the Timer 2 registers with the 16-bit value in the RCAP2L and RCAP2H registers, which are preset by software. If EXEN2 = 1, then Timer 2 performs the same way, but a 1-to-0 transition at external input T2EX also triggers the 16-bit reload and sets EXF2.

The auto-reload mode is illustrated in Figure 13. The baud rate generator mode is selected by RCLK = 1

and/or TCLK = 1. This mode is described in conjunction with the serial port (Figure 14).

OSC

T2EX PIN

DIVIDE 12

T2 PIN

C/T2 = 0

C/T2 = 1

TRANSITION

DETECTOR

EXEN2

TL2

(8 BITS)

CONTROL

TR2

CAPTURE

RCAP2L

CONTROL

TH2

(8 BITS)

RCAP2H

Figure 12. Timer 2 In Capture Mode

TF2

TIMER 2

INTERRUPT

EXF2

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OSC

T2EX PIN

T2 PIN

DIVIDE 2

DIVIDE 12

TRANSITION

NOTE: OSC FREQ.

IS DIV BY 2, NOT 12

TRANSITION

DETECTOR

EXEN2

C/T2 = 0

C/T2 = 1

C/T2 = 0

C/T2 = 1

CONTROL

TR2

RELOAD

TL2

(8 BITS)

RCAP2L

TH2

(8 BITS)

RCAP2H

Figure 13. Timer 2 in Auto-Reload Mode

CONTROL

TR2

TL2

(8 BITS)

RCAP2L

TH2

(8 BITS)

RCAP2H

RELOAD

"1"

TF2

EXF2

TIMER 1

OVERFLOW

DIVIDE 2

"0"

"0""1"

"1"

INTERRUPT

SMOD

RCLK

DIVIDE 16

TCLK

DIVIDE 16

TIMER 2

RX CLOCK

TX CLOCK

T2EX PIN

CONTROL

EXEN2

EXF2

Figure 14. Timer 2 in Baud Rate Generator Mode

Note:

1. T2EX can be used as an additional external interrupt.

TIMER 2

INTERRUPT

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Timer Set-Up

Tables 3 through 6 give TMOD values that can be used to set up Timers in different modes.

It assumes that only one timer is used at a time. If Timers 0 and 1 must run simultaneously in any mode, the value in TMOD for Timer 0 must be ORed with the value shown for Timer 1 (Tables 5 and 6).

For example, if Timer 0 must run in Mode 1 GATE (external control), and Timer 1 must run in Mode 2 COUNTER, then the value that must be loaded into TMOD is 69H (09H from Table 3 ORed with 60H from Table 6).

Moreover, it is assumed that the user is not ready at this point to turn the timers on and will do so at another point in the program by setting bit TRx (in TCON) to 1.

Table 3. Timer/Counter 0 Used as a Timer

TMOD

Mode Timer 0 Internal External

Function Control

0 13-Bit Timer 00H 08H 1 16-Bit Timer 01H 09H 2 8-Bit Auto-Reload 02H 0AH 3 Two 8-Bit Timers 03H 0BH

(1)

Control

(2)

Table 5. Timer/Counter 1 Used as a Timer

TMOD

Mode Timer 1 Internal External

Function Control

(1)

Control

(2)

0 13-Bit Timer 00H 80H 1 16-Bit Timer 10H 90H 2 8-Bit Auto-Reload 20H A0H 3 Does Not Run 30H B0H

Table 6. Timer/Counter 1 Used as a Counter

TMOD

Mode Timer 1 Internal External

Function Control

(1)

Control

(2)

0 13-Bit Timer 40H C0H 1 16-Bit Timer 50H D0H 2 8-Bit Auto-Reload 60H E0H 3 Not Available — —

Notes:

1. The Timer is turned ON/OFF by setting/clearing bit TR1 in the

software.

2. The Timer is turned ON/OFF by the 1 to 0 transition on INT1

(P3.3) when TR1 = 1 (hardware control).

Table 4. Timer/Counter 0 Used as a Counter

TMOD

Mode Timer 0 Internal External

Function Control

(1)

Control

(2)

0 13-Bit Timer 04H 0CH 1 16-Bit Timer 05H 0DH 2 8-Bit Auto-Reload 06H 0EH 3 One 8-Bit Counter 07H 0FH

Notes:

1. The Timer is turned ON/OFF by setting/clearing bit TR0 in the software.

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Timer/Counter 2 Set-Up

Except for the baud rate generator mode, the values given for T2C0N do not include the setting of the TR2 bit. Therefore, bit TR2 must be set separately to turn the Timer on.

Table 7. Timer/Counter 2 Used as a Timer

T2CON

Mode Internal External

Control

16-Bit Auto-Reload 00H 08H

16-Bit Capture 01H 09H Baud Rate Generator Receive 34H 36H

and Transmit Same Baud Rate Receive Only 24H 26H Transmit Only 14H 16H

Table 8. Timer/Counter 2 Used as a Counter

Mode Internal External

Control

16-Bit Auto-Reload 02H 0AH

16-Bit Capture 03H 0BH

Notes:

1. Capture/Reload occurs only on Timer/Counter overflow.

2. Capture/Reload occurs on Timer/Counter overflow and a 1 to 0 transition on T2EX (P1.1) pin except when Timer 2 is used in the baud rate generating mode.

(1)

TMOD

(1)

Control

(2)

SERIAL INTERFACE

The Serial port is full duplex, which means it can transmit and receive simultaneously. It is also receive-buffered, which means it can begin receiving a second byte before a previously received byte has been read from the receive register. (However, if the first byte still has not been read when reception of the second byte is complete, one of the bytes will be lost.) The serial port receive and transmit registers are both accessed at Special Function Register SBUF. Writing to SBUF loads the transmit register, and reading SBUF accesses a physically separate receive register.

The serial port can operate in the following four modes:

Mode 0:

Serial data enters and exits through RXD. TXD outputs the shift clock. Eight data bits are transmitted/received, with the LSB first. The baud rate is fixed at 1/12 the oscillator frequency (see Figure 15).

Mode 1:

Ten bits are transmitted (through TXD) or received (through RXD): a start bit (0), eight data bits (LSB first), and a stop bit (1). On receive, the stop bit goes into RB8 in Special Function Register SCON. The baud rate is variable (see Figure 16).

Mode 2:

Eleven bits are transmitted (through TXD) or received (through RXD): a start bit (0), eight data bits (LSB first), a programmable ninth data bit, and a stop bit (1). On transmit, the ninth data bit (TB8 in SCON) can be assigned the value of 0 or 1. Or, for example, the parity bit (P, in the PSW) can be moved into TB8. On receive, the ninth data bit goes into RB8 in Special Function Register SCON, while the stop bit is ignored. The baud rate is programmable to either 1/32 or 1/64 the oscillator frequency (see Figure 17).

Mode 3:

Eleven bits are transmitted (through TXD) or received (through RXD): a start bit (0), eight data bits (LSB first), a programmable ninth data bit, and a stop bit (1). In fact, Mode 3 is the same as Mode 2 in all respects except the baud rate, which is variable in Mode 3 (see Figure 18).

In all four modes, transmission is initiated by any instruction that uses SBUF as a destination register. Reception is initiated in Mode 0 by the condition RI = 0 and REN = 1. Reception is initiated in the other modes by the incoming start bit if REN = 1.

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MULTIPROCESSOR COMMUNICATIONS

Modes 2 and 3 have a special provision for multiprocessor communications. In these modes, nine data bits are received, followed by a stop bit. The ninth bit goes into RB8; then comes a stop bit. The port can be programmed such that when the stop bit is received, the serial port interrupt is activated only if RB8 = 1. This feature is enabled by setting bit SM2 in SCON.

The following example shows how to use the serial interrupt for multiprocessor communications. When the master processor must transmit a block of data to one of several slaves, it first sends out an address byte that identifies the target slave. An address byte differs from a data byte in that the ninth bit is 1 in an address byte and 0 in a data byte. With SM2 = 1, no slave is interrupted by a data byte. An address byte, however, interrupts all slaves, so that each slave can examine the received byte and see if it is being addressed. The addressed slave clears its SM2 bit and prepares to receive the data bytes that follows. The slaves that are not addressed set their SM2 bits and ignore the data bytes.

SM2 has no effect in Mode 0 but can be used to check the validity of the stop bit in Mode 1. In a Mode 1 reception, if SM2 = 1, the receive interrupt is not activated unless a valid stop bit is received.

Baud Rates

The baud rate in Mode 0 is fixed as shown in the following equation.

Using the Timer 1 to Generate Baud Rates

When Timer 1 is the baud rate generator, the baud rates in Modes 1 and 3 are determined by the Timer 1 overflow rate and the value of SMOD according to the following equation.

Mode 1, 3 2 Baud Rate =

The Timer 1 interrupt should be disabled in this application. The Timer itself can be configured for either timer or counter operation in any of its 3 running modes. In the most typical applications, it is configured for timer operation in auto-reload mode (high nibble of TMOD = 0010B). In this case, the baud rate is given by the following formula.

Mode 1,3 2 Baud Rate

Programmers can achieve very low baud rates with Timer 1 by leaving the Timer 1 interrupt enabled, configuring the Timer to run as a 16-bit timer (high nibble of TMOD = 0001B), and using the Timer 1 interrupt to do a 16-bit software reload.

Table 9 lists commonly used baud rates and how they can be obtained from Timer 1.

SMOD

32 12x [256-(TH1)]

(Timer 1 Overflow Rate)

Oscillator Frequency

Mode 0 Baud Rate = The baud rate in Mode 2 depends on the value of the

SMOD bit in Special Function Register PCON. If SMOD = 0 (the value on reset), the baud rate is 1/64 of the oscillator frequency. If SMOD = 1, the baud rate is 1/32 of the oscillator frequency, as shown in the following equation.

Mode 2 Baud Rate =

In the IS80C51/31, the Timer 1 overflow rate determines the baud rates in Modes 1 and 3. In the IS80C52/32, these baud rates can be determined by Timer 1, Timer 2, or both (one for transmit and the other for receive).

SMOD

x (Oscillator Frequency)

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Using Timer 2 to Generate Baud Rates

In the IS80C52/32, setting TCLK and/or RCLK in T2CON selects Timer 2 as the baud rate generator. Under these conditions, the baud rates for transmit and receive can be simultaneously different. Setting RCLK and/or TCLK puts Timer 2 into its baud rate generator mode, as shown in Figure 14.

The baud rate generator mode is similar to the auto-reload mode, in that a rollover in TH2 reloads the Timer 2 registers with the 16-bit value in the RCAP2H and RCAP2L registers, which are preset by software.

In this case, the baud rates in Mode 1 and 3 are determined by the Timer 2 overflow rate according to the following equation.

Modes 1, 3 Baud Rate =

Timer 2 can be configured for either timer or counter operation. In the most typical applications, it is configured for timer operation (C/T2 = 0). Normally, a timer increments every machine cycle (thus at 1/12 the oscillator frequency), but timer operation is a different for Timer 2 when it is used as a baud rate generator. As a baud rate generator, Timer 2 increments every state time (thus at 1/2 the oscillator frequency). In this case, the baud rate is given by the following formula.

Timer 2 Overflow Rate

Figure 13 shows Timer 2 as a baud rate generator. This figure is valid only if RCLK + TCLK = 1 in T2CON. A rollover in TH2 does not set TF2 and does no generate an interrupt. Therefore, the Timer 2 interrupt does not have to be disabled when Timer 2 is in the baud rate generator mode. If EXEN2 is set, a 1-to-0 transition in T2EX sets EXF2 but does not cause a reload from (RCAP2H, RCAP2L) to (TH2, TL2). Thus, when Timer 2 is used as a baud rate generator, T2EX can be used as an extra external interrupt.

When Timer 2 is running (TR2 = 1) as a timer in the baud rate generator mode, programmers should not read from or write to TH2 or TL2. Under these conditions, Timer 2 is incremented every state time, and the results of a read or write may not be accurate. The RCAP registers may be read, but should not be written to, because a write might overlap a reload and cause write and/or reload errors. Turn Timer 2 off (clear TR2) before accessing the Timer 2 or RCAP registers, in this case.

Modes 1, 3 Oscillator Frequency Baud Rate

Where (RCAP2H, RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16-bit unsigned integer.

Table 9. Commonly Used Baud Rates Generated by Timer 1

Baud Rate fOSC SMOD C/T Mode Reload Value

Mode 0 Max: 1 MHz 12 MHz X X X X

Mode 2 Max: 375K 12 MHz 1 X X X

Modes 1, 3: 62.5K 12 MHz 1 0 2 FFH

32x [65536 – (RCAP2H, RCAP2L)]

Timer 1

19.2K 11.059 MHz 1 0 2 FDH

9.6K 11.059 MHz 0 0 2 FDH

4.8K 11.059 MHz 0 0 2 FAH

2.4K 11.059 MHz 0 0 2 F4H

1.2K 11.059 MHz 0 0 2 E8H

137.5 11.986 MHz 0 0 2 1DH 110 6 MHz 0 0 2 72H 110 12 MHz 0 0 1 FEEBH

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More About Mode 0

Serial data enters and exits through RXD. TXD outputs the shift clock. Eight data bits are transmitted/received, with the LSB first. The baud rate is fixed at 1/12 the oscillator frequency.

Figure 15 shows a simplified functional diagram of the serial port in Mode 0 and associated timing.

Transmission is initiated by any instruction that uses SBUF as a destination register. The "write to SBUF" signal at S6P2 also loads a 1 into the ninth position of the transmit shift register and tells the TX Control block to begin a transmission. The internal timing is such that one full machine cycle will elapse between "write to SBUF" and activation of SEND.

SEND transfer the output of the shift register to the alternate output function line of P3.0, and also transfers SHIFT CLOCK to the alternate output function line of P3.1. SHIFT CLOCK is low during S3, S4, and S5 of every machine cycle, and high during S6, S1, and S2. At S6P2 of every machine cycle in which SEND is active, the contents of the transmit shift register are shifted one position to the right.

As data bits shift out to the right, 0s come in from the left. When the MSB of the data byte is at the output position of the shift register, the 1 that was initially loaded into the ninth position is just to the left of the MSB, and all positions to the left of that contain 0s. This condition flags the TX Control block to do one last shift, then deactivate SEND and set TI. Both of these actions occur at S1P1 of the tenth machine cycle after "write to SBUF."

Reception is initiated by the condition REN = 1 and RI = 0. At S6P2 of the next machine cycle, the RX Control unit writes the bits 11111110 to the receive shift register and activates RECEIVE in the next clock phase.

RECEIVE enables SHIFT CLOCK to the alternate output function line of P3.1. SHIFT CLOCK makes transitions at S3P1 and S6P1 of every machine cycle. At S6P2 of every machine cycle in which RECEIVE is active, the contents of the receive shift register are shifted on position to the left. The value that comes in from the right is the value that was sampled at the P3.0 pin at S5P2 of the same machine cycle.

As data bits come in from the right, 1s shift out to the left. When the 0 that was initially loaded into the right-most position arrives at the left-most position in the shift register, it flags the RX Control block to do one last shift and load SBUF. At S1P1 of the 10th machine cycle after the write to SCON that cleared RI, RECEIVE is cleared and RI is set.

More About Mode 1

Ten bits are transmitted (through TXD), or received (through RXD): a start bit (0), eight data bits (LSB first), and a stop bit (1). On receive, the stop bit goes into RB8 in SCON. In the IS80C52/32 the baud rate is determined either by the Timer 1 overflow rate, the Timer 2 overflow rate, or both. In this case, one Timer is for transmit, and the other is for receive.

Figure 16 shows a simplified functional diagram of the serial port in Mode 1 and associated timings for transmit and receive.

Transmission is initiated by any instruction that uses SBUF as a destination register.

The "write to =SBUF" signal also loads a 1 into the ninth bit position of the transmit shift register and flags the TX control unit that a transmission is requested. Transmission actually commences at S1P1 of the machine cycle following the next rollover in the divide-by-16 counter. Thus, the bit times are synchronized to the divide-by-16 counter, not to the "write to SBUF" signal.

The transmission begins when SEND is activated, which puts the start bit at TXD. One bit time later, DATA is activated, which enables the output bit of the transmit shift register to TXD. The first shift pulse occurs one bit time after that.

As data bits shift out to the right, 0s are clocked in from the left. When the MSB of the data byte is at the output position of the shift register, the 1 that was initially loaded into the ninth position is just to the left of the MSB, and all positions to the left of that contain 0s. This condition flags the TX Control unit to do one last shift, then deactivate SEND and set TI. This occurs at the tenth divide-by-16 rollover after "write to SBUF".

Reception is initiated by a 1-to-0 transition detected at RXD. For this purpose, RXD is sampled at a rate of 16 times the established baud rate. When a transition is detected, the divide-by-16 counter is immediately reset, and 1FFH is written into the input shift register. Resetting the divide-by-16 counter aligns its rollovers with the boundaries of the incoming bit times.

The 16 states of the counter divide each bit time into 16th. At the seventh, eighth, and ninth counter states of each bit time, the bit detector samples the value of RXD. The value accepted is the value that was seen in at least two of the three samples. This is done to reject noise. In order to reject false bits, if the value accepted during the first bit time is not 0, the receive circuits are reset and the unit continues looking for another 1-to-0 transition. If the start bit is valid, it is shifted into the input shift register, and reception of the rest of the frame proceeds.

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ISSI

As data bits come in from the right, 1s shift to the left. When the start bit arrives at the leftmost position in the shift register, (which is a 9-bit register in Mode 1), it flags the RX Control block to do one last shift, load SBUF and RB8, and set RI. The signal to load SBUF and RB8 and to set RI is generated if, and only if, the following conditions are met at the time the final shift pulse is generated.

1. RI = 0 and

2. Either SM2 = 0, or the received stop bit =1

If either of these two conditions is not met, the received frame is irretrievably lost. If both conditions are met, the stop bit goes into RB8, the eight data bits go into SBUF, and RI is activated. At this time, whether or not the above conditions are met, the unit continues looking for a 1-to0 transition in RXD.

More About Modes 2 and 3

Eleven bits are transmitted (through TXD), or received (through RXD): a start bit (0), 8 data bits (LSB first), a programmable ninth data bit, and a stop bit (1). On transmit, the ninth data bit (TB8) can be assigned the value of 0 or 1. On receive, the ninth data bit goes into RB8 in SCON. The baud rate is programmable to either 1/32 or 1/64 of the oscillator frequency in Mode 2. Mode 3 may have a variable baud rate generated from either Timer 1 or 2, depending on the state of TCLK and RCLK.

Figures 17 and 18 show a functional diagram of the serial port in Modes 2 and 3. The receive portion is exactly the same as in Mode 1. The transmit portion differs from Mode 1 only in the ninth bit of the transmit shift register.

Transmission is initiated by any instruction that uses SBUF as a destination register. The "write to SBUF" signal also loads TB8 into the ninth bit position of the transmit shift register and flags the TX Control unit that a transmission is requested. Transmission commences at S1P1 of the machine cycle following the next rollover in the divide-by-16 counter. Thus, the bit times are synchronized to the divide-by-16 counter, not to the "write to SBUF" signal.

The transmission begins when SEND is activated, which puts the start bit at TXD. One bit timer later, DATA is activated, which enables the output bit of the transmit shift register to TXD. The first shift pulse occurs one bit time after that. The first shift clocks a 1 (the stop bit) into the ninth bit position of the shift register. Thereafter, only 0s are clocked in. Thus, as data bits shift out to the right, 0s are clocked in from the left. When TB8 is at the output position of the shift register, then the stop bit is just to the left of TB8, and all positions to the left of that contain 0s. This condition flags the TX Control unit to do one last shift, then deactivate SEND and set TI. This occurs at the 11th divide-by-16 rollover after "write to SBUF".

At the seventh, eighth, and ninth counter states of each bit time, the bit detector samples the value of RXD. The value accepted is the value that was seen in at least two of the three samples. If the value accepted during the first bit time is not 0, the receive circuits are reset and the unit continues looking for another 1-to-0 transition. If the start bit proves valid, it is shifted into the input shift register, and reception of the rest of the frame proceeds.

As data bits come in from the right, Is shift out to the left. When the start bit arrives at the leftmost position in the shift register (which in Modes 2 and 3 is a 9-bit register), it flags the RX Control block to do one last shift, load SBUF and RB8, and set RI. The signal to load SBUF and RB8 and to set RI is generated if, and only if, the following conditions are met at the time the final shift pulse is generated:

1. RI = 0, and

2. Either SM2 = 0 or the received 9th data bit = 1

If either of these conditions is not met, the received frame is irretrievably lost, and RI is not set. If both conditions are met, the received ninth data bit goes into RB8, and the first eight data bits go into SBUF. One bit time later, whether the above conditions were met or not, the unit continues looking for a 1-to-0 transition at the RXD input.

Note that the value of the received stop bit is irrelevant to SBUF, RB8, or RI.

Table 10. Serial Port Setup

Mode SCON SM2Variation

0 10H 1 50H 2 90H 3 D0H 0NA 1 70H 2 B0H 3 F0H

Single Processor

Environment

(SM2 = 0)

Multiprocessor

Environment

(SM2 = 1)

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IS80C52 IS80C32

WRITE

SBUF

ISSI

ZERO DETECTOR

SBUF

SHIFT

RXD P3.0 ALT OUTPUT FUNCTION

START

INTERRUPT

REN

S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1

TX CLOCK

SERIAL

PORT

RX CLOCK START

TX CONTROL

RX CONTROL

1 1 1 1 1 1 1 0

INPUT SHIFT REG.

LOAD

SBUF

READ

SBUF

IS80C52/32 INTERNAL BUS

SHIFT

SEND

RECEIVE

SHIFT

CLOCK

TXD P3.1 ALT OUTPUT FUNCTION

RXD P3.0 ALT INPUT FUNCTION

ALE

SEND SHIFT

RXD (D

TXD (SHIFT CLOCK)

RI RECEIVE

SHIFT

RXD (D

TXD (SHIFT CLOCK)

WRITE TO SBUF

S6P2

OUT)

WRITE TO SCON (CLEAR RI)

IN)

D0 D1 D2 D3 D5 D6 D7

S6P1S3P1

S5P2

D1 D2 D3 D5 D6 D7

Figure 15. Serial Port Mode 0

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TRANSMIT

RECEIVE

IS80C52 IS80C32

ISSI

TIMER 1

OVERFLOW

÷ 2

SMOD

= 0

RCLK

TCLK

SMOD

= 1

"0" "1"

"0"

TIMER 2

OVERFLOW

"1"

SAMPLE

RXD

WRITE

SBUF

÷ 16

1-TO-0

TRANSITION

DETECTOR

TB8

START RX CLOCK

÷ 16

RX CLOCK START

BIT

DETECTOR

IS80C52/32 INTERNAL BUS

SBUF

ZERO DETECTOR

SHIFT

TX CONTROL

RX CONTROL

LOAD SBUF

DATA

SEND

LOAD

SBUF

SHIFT

1FFH

INPUT SHIFT REG.

(9 BITS)

SERIAL PORT INTERRUPT

SHIFT

TXD

TX CLOCK

WRITE TO SBUF

SEND

DATA

SHIFT

TXD

RECEIVE

S1P1

START

BIT

CLOCK

RXD

BIT DETECTOR SAMPLE TIMES

SHIFT

READ SBUF

IS80C52/32 INTERNAL BUS

D0 D1 D2 D3 D5 D6

÷ 16 RESET

START

D0 D1 D2 D3 D5 D6

BIT

SBUF

TRANSMIT

STOP BIT

Figure 16. Serial Port Mode 1

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IS80C52 IS80C32

ISSI

PHASE 2 CLOCK

OSC

(1/2 f

MODE 2

÷ 2

(SMOD IS PCON. 7)

RXD

)

SMOD 1

SMOD 0

SAMPLE

WRITE

SBUF

÷ 16

1-TO-0

TRANSITION

DETECTOR

TB8

START TX CLOCK

÷ 16

START

BIT

DETECTOR

IS80C52/32 INTERNAL BUS

STOP BIT GEN

TX CONTROL

CLOCK

RX CONTROL

SBUF

ZERO DETECTOR

SHIFT

INPUT SHIFT REG.

LOAD SBUF

DATA

SEND

LOAD SBUF

SHIFT

1FFH

(9 BITS)

SERIAL PORT INTERRUPT

SHIFT

TXD

WRITE TO SBUF

DATA

SHIFT

RECEIVE

CLOCK

SEND S1P1

START

BIT

STOP BIT GEN

CLOCK

RXD

BIT DETECTOR SAMPLE TIMES

SHIFT

READ

SBUF

IS80C52/32 INTERNAL BUS

D0 D1 D2 D3 D5 D6

÷ 16 RESET

START

D0 D1 D2 D3 D5 D6

BIT

Figure 17. Serial Port Mode 2

SBUF

TRANSMIT

D7 TB8

STOP BITTXD

RB8

STOP

BIT

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IS80C52 IS80C32

TIMER 1

OVERFLOW

÷ 2

SMOD

= 0

SMOD

= 1

TIMER 2

OVERFLOW

WRITE

SBUF

TB8

IS80C52/32 INTERNAL BUS

ZERO DETECTOR

SBUF

ISSI

TXD

TCLK

RCLK

"0" "1"

"0"

CLOCK

"1"

RXD

SAMPLE

TRANSITION

DETECTOR

1-TO-0

÷ 16

START RX CLOCK

÷ 16

RX CLOCK START

BIT

DETECTOR

TX CONTROL

RX CONTROL

SHIFT

INPUT SHIFT REG.

LOAD SBUF

READ

SBUF

IS80C52/32 INTERNAL BUS

DATA

SEND

LOAD SBUF

SHIFT

1FFH

(9 BITS)

SBUF

SERIAL PORT INTERRUPT

SHIFT

WRITE TO SBUF

SEND

DATA

SHIFT

RECEIVE

S1P1

START

BIT

STOP BIT GEN

CLOCK

RXD

BIT DETECTOR SAMPLE TIMES

SHIFT

D0 D1 D2 D3 D5 D6

÷ 16 RESET

START

D0 D1 D2 D3 D5 D6

BIT

Figure 18. Serial Port Mode 3

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TRANSMIT

TB8D7

STOP BITTXD

RB8

STOP

BIT

MC004-1D

11/19/98

IS80C52 IS80C32

INTERRUPT SYSTEM

ISSI

The IS80C52/32 provides six interrupt sources: two external interrupts, three timer interrupts, and a serial port interrupt. These are shown in Figure 19.

The External Interrupts INT0 and INT1 can each be either level-activated or transition-activated, depending on bits IT0 and IT1 in Register TCON. The flags that actually generate these interrupts are the IE0 and IE1 bits in TCON. When the service routine is vectored to, hardware clears the flag that generated an external interrupt only if the interrupt was transition-activated. If the interrupt was level-activated, then the external requesting source (rather than the on-chip hardware) controls the request flag.

The Timer 0 and Timer 1 Interrupts are generated by TF0 and TF1, which are set by a rollover in their respective Timer/Counter registers (except for Timer 0 in Mode 3). When a timer interrupt is generated, the on-chip hardware clears the flag that generated it when the service routine is vectored to.

The Serial Port Interrupt is generated by the logical OR of RI and TI. Neither of these flags is cleared by hardware

when the service routine is vectored to. In fact, the service routine normally must determine whether RI or TI generated the interrupt, and the bit must be cleared in software.

In the IS80C52/32, the Timer 2 Interrupt is generated by the logical OR of TF2 and EXF2. Neither of these flags is cleared by hardware when the service routine is vectored to. In fact, the service routine may have to determine whether TF2 or EXF2 generated the interrupt, and the bit must be cleared in software.

All of the bits that generate interrupts can be set or cleared by software, with the same result as though they had been set or cleared by hardware. That is, interrupts can be generated and pending interrupts can be canceled in software.

Each of these interrupt sources can be individually enabled or disabled by setting or clearing a bit in Special Function Register IE (interrupt enable) at address 0A8H. As well as individual enable bits for each interrupt source, there is a global enable/disable bit that is cleared to disable all interrupts or set to turn on interrupts (see SFR IE).

POLLING

HARDWARE

INT0

INT1

T2EX

TCON.1

EXTERNAL

INT RQST 0

TCON.5

TIMER/COUNTER 0

TCON.3

EXTERNAL

INT RQST 1

TCON.7

TIMER/COUNTER 1

INTERNAL

SERIAL

PORT

TIMER/

COUNTER 2

SCON.0

SCON.1

T2CON.7

TF2

T2CON.6

EXF2

IE0

TF0

IE1

TF1

IE.0

EX0 IE.1

ET0 IE.2

EX1 IE.3

ET1 IE.4

IE.5 IP.5

IE.7

IP.0

PX0 IP.1

PT0 IP.2

PX1 IP.3

PT1 IP.4

PT2ET2 EA

SOURCE

I.D.

SOURCE

I.D.

HIGH PRIORITY

INTERRUPT

REQUEST

VECTOR

LOW PRIORITY

INTERRUPT

REQUEST

VECTOR

Figure 19. Interrupt System

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ISSI

Priority Level Structure

Each interrupt source can also be individually programmed to one of two priority levels by setting or clearing a bit in Special Function Register IP (interrupt priority) at address 0B8H. IP is cleared after a system reset to place all interrupts at the lower priority level by default. A lowpriority interrupt can be interrupted by a high-priority interrupt but not by another low-priority interrupt. A highpriority interrupt can not be interrupted by any other interrupt source.

If two requests of different priority levels are received simultaneously, the request of higher priority level is serviced. If requests of the same priority level are received simultaneously, an internal polling sequence determines which request is serviced. Thus, within each priority level there is a second priority structure determined by the polling sequence, as follows:

Source Priority Within Level

1. IE0 (Highest)

2. TF0

3. IE1

4. TF1

5. RI + TI

6. TF2 + EXF2 (Lowest)

Note that the "priority within level" structure is only used to resolve

level

simultaneous requests of the same priority

in the Response Timer Section). If one of the flags was in a set condition at S5P2 of the preceding cycle, the polling cycle will find it and the interrupt system will generate an LCALL to the appropriate service routine, provided this hardware generated LCALL is not blocked by any of the following conditions:

1. An interrupt of equal or higher priority level is already in progress.

2. The current (polling) cycle is not the final cycle in the execution of the instruction in progress.

3. The instruction in progress is RETI or any write to the IE or IP registers.

Any of these three conditions will block the generation of the LCALL to the interrupt service routine. Condition 2 ensures that the instruction in progress will be completed before vectoring to any service routine. Condition 3 ensures that if the instruction in progress is RETI or any access to IE or IP, then at least one more instruction will be executed before any interrupt is vectored to.

The polling cycle is repeated with each machine cycle, and the values polled are the values that were present at S5P2 of the previous machine cycle. If an active interrupt flag is not being serviced because of one of the above conditions and is not still active when the blocking condition is removed, the denied interrupt will not be serviced. In other words, the fact that the interrupt flag was once active but not serviced is not remembered. Every polling cycle is new. The polling cycle/LCALL sequence is illustrated in Figure 20.

How Interrupts Are Handled

The interrupt flags are sampled at S5P2 of every machine cycle. The samples are polled during the following machine cycle (the Timer 2 interrupt cycle is different, as described

INTERRUPT

GOES ACTIVE

S5P2

INTERRUPT LATCHED

Figure 20. Interrupt Response Timing Diagram

INTERRUPTS

ARE POLLED

Note that if an interrupt of higher priority level goes active prior to S5P2 of the machine cycle labeled C3 in Figure 20, then in accordance with the above rules it will be serviced during C5 and C6, without any instruction of the lower priority routine having been executed.

C4C3C2

LONG CALL TO

INTERRUPT

VECTOR ADDRESS

INTERRUPT

ROUTINE

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Thus, the processor acknowledges an interrupt request by executing a hardware-generated LCALL to the appropriate servicing routine. In some cases it also clears the flag that generated the interrupt, and in other cases it does not. It never clears the Serial Port or Timer 2 flags. This must be done in the user's software. The processor clears an external interrupt flag (IE0 or IE1) only if it was transition-activated. The hardware-generated LCALL pushes the contents of the Program Counter onto the stack (but it does not save the PSW) and reloads the PC with an address that depends on the source of the interrupt being serviced, as follows:

Interrupt Interrupt Cleared by Vector

Source Request Bits Hardware Address

INT0

Timer 0 TF0 Yes 000BH

INT1

Timer 1 TF1 Yes 001BH

Serial Port RI, TI No 0023H

Timer 2 TF2, EXF2 No 002BH System RST 0000H

Reset

Execution proceeds from that location until the RETI instruction is encountered. The RETI instruction informs the processor that this interrupt routine is no longer in progress, then pops the top two bytes from the stack and reloads the Program Counter. Execution of the interrupted program continues from where it left off.

Note that a simple RET instruction would also have returned execution to the interrupted program, but it would have left the interrupt control system thinking an interrupt was still in progress.

IE0 No (level) 0003H

Yes (trans.)

IE1 No (level) 0013H

Yes (trans.)

SFR Register and

Interrupt Flag Bit Position

External 0 IE0 TCON.1 External 1 IE1 TCON.3 Timer 1 TF1 TCON.7 Timer 0 TF0 TCON.5 Serial Port TI SCON.1 Serial Port RI SCON.0Timer 2

TF2 T2CON.7 Timer 2 EXF2 T2CON.6

When an interrupt is accepted the following action occurs:

1. The current instruction completes operation.

2. The PC is saved on the stack.

3. The current interrupt status is saved internally.

4. Interrupts are blocked at the level of the interrupts.

5. The PC is loaded with the vector address of the ISR (interrupts service routine).

6. The ISR executes.

The ISR executes and takes action in response to the interrupt. The ISR finishes with RETI (return from interrupt) instruction. This retrieves the old value of the PC from the stack and restores the old interrupt status. Execution of the main program continues where it left off.

External Interrupts

The external sources can be programmed to be levelactivated or transition-activated by setting or clearing bit IT1 or IT0 in Register TCON. If ITx= 0, external interrupt x is triggered by a detected low at the INTx pin. If ITx = 1, external interrupt x is edge-triggered. In this mode if successive samples of the INTx pin show a high in one cycle and a low in the next cycle, interrupt request flag IEx in TCON is set. Flag bit IEx then requests the interrupt.

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Since the external interrupt pins are sampled once each machine cycle, an input high or low should hold for at least 12 oscillator periods to ensure sampling. If the external interrupt is transition-activated, the external source has to hold the request pin high for at least one machine cycle, and then hold it low for at least one machine cycle to ensure that the transition is seen so that interrupt request flag IEx will be set. IEx will be automatically cleared by the CPU when the service routine is called.

If the external interrupt is level-activated, the external source has to hold the request active until the requested interrupt is actually generated. Then the external source must deactivate the request before the interrupt service routine is completed, or else another interrupt will be generated.

Response Time

The INT0 and INT1 levels are inverted and latched into the interrupt flags IE0 and IE1 at S5P2 of every machine cycle. Similarly, the Timer 2 flag EXF2 and the Serial Port flags RI and TI are set at S5P2. The values are not actually polled by the circuitry until the next machine cycle.

The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in which the timers overflow. The values are then polled by the circuitry in the next cycle. However, the Timer 2 flag TF2 is set at S2P2 and is polled in the same cycle in which the timer overflows.

Single-Step Operation

The IS80C52/32 interrupt structure allows single-step execution with very little software overhead. As previously noted, an interrupt request will not be serviced while an interrupt of equal priority level is still in progress, nor will it be serviced after RETI until at least one other instruction has been executed. Thus, once an interrupt routine has been entered, it cannot be reentered until at least one instruction of the interrupted program is executed. One way to use this feature for single-step operation is to program one of the external interrupts (for example, to be level-activated. The service routine for the interrupt will terminate with the following code:

JNB P3.2,$ ;Wait Here Till JB P3.2,$ ;Now Wait Here Till it Goes Low RETI ;Go Back and Execute One

Instruction

If the

INT0

pin, which is also the P3.2 pin, is held normally low, the CPU will go right into the External Interrupt 0 routine and stay there until high-to-low). Then it will execute RETI, go back to the task program, execute one instruction, and immediately reenter the External Interrupt 0 routine to await the next pulsing of P3.2. One step of the task program is executed each time P3.2 is pulsed.

INT0

Goes High

is pulsed (from low-to-

INT0

)

If a request is active and conditions are right for it to be acknowledged, a hardware subroutine call to the requested service routine will be the next instruction executed. The call itself takes two cycles. Thus, a minimum of three complete machine cycles elapsed between activation of an external interrupt request and the beginning of execution of the first instruction of the service routine. Figure 19 shows response timings.

A longer response time results if the request is blocked by one of the three previously listed conditions. If an interrupt of equal or higher priority level is already in progress, the additional wait time depends on the nature of the other interrupt's service routine. If the instruction in progress is not in its final cycle, the additional wait time cannot be more than three cycles, since the longest instructions (MUL and DIV) are only four cycles long. If the instruction in progress is RETI or an access to IE or IP, the additional wait time cannot be more than five cycles (a maximum of one more cycle to complete the instruction in progress, plus four cycles to complete the next instruction if the instruction is MUL or DIV).

Thus, in a single-interrupt system, the response time is always more than three cycles and less than nine cycles.

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ISSI

OTHER INFORMATION Reset

The reset input is the RST pin, which is the input to a Schmitt Trigger.

A reset is accomplished by holding the RST pin high for at least two machine cycles (24 oscillator periods),

oscillator is running

internal reset, with the timing shown in Figure 21. The external reset signal is asynchronous to the internal

clock. The RST pin is sampled during State 5 Phase 2 of every machine cycle. The port pins will maintain their current activities for 19 oscillator periods after a logic 1 has been sampled at the RST pin; that is, for 19 to 31 oscillator periods after the external reset signal has been applied to the RST pin.

The internal reset algorithm writes 0s to all the SFRs except the port latches, the Stack Pointer, and SBUF. The port latches are initialized to FFH, the Stack Pointer to 07H, and SBUF is indeterminate. Table 11 lists the SFRs and their reset values.

Then internal RAM is not affected by reset. On power-up the RAM content is indeterminate.

. The CPU responds by generating an

while the

Table 11. Reset Values of the SFR's

SFR Name Reset Value

PC 0000H

ACC 00H

B 00H

PSW 00H

SP 07H

DPTR 0000H

P0-P3 FFH

IP XX000000B IE 0X000000B

TMOD 00H

TCON 00H

T2CON 00H

TH0 00H

TL0 00H

TH1 00H

TL1 00H

TH2 00H

TL2 00H

RCAP2H 00H

RCAP2L 00H

SCON 00H

SBUF Indeterminate

PCON 0XXX0000B

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IS80C52 IS80C32

Power-on Reset

An automatic reset can be obtained when VCC goes through a 10µF capacitor and GND through an 8.2K resistor, providing the VCC rise time does not exceed 1 msec 10 msec. This power-on reset circuit is shown in Figure

21. The CMOS devices do not require the 8.2K pulldown resistor, although its presence does no harm.

When power is turned on, the circuit holds the RST pin high for an amount of time that depends on the value of the capacitor and the rate at which it charges. To ensure a good reset, the RST pin must be high long enough to allow the oscillator time to start-up (normally a few msec) plus two machine cycles.

and the oscillator start-up time does not exceed

Vcc

10µf

8.2K Ω

ISSI

Vcc

IS80C52/32

RST

Note that the port pins will be in a random state until the oscillator has start and the internal reset algorithm has written 1s to them.

With this circuit, reducing VCC quickly to 0 causes the RST pin voltage to momentarily fall below 0V. However, this voltage is internally limited, and will not harm the device.

12 OSC. PERIODS

S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4

RST

SAMPLE

RST

ALE

SAMPLE RST

GND

Figure 21. Power-On Reset Circuit

INTERNAL RESET SIGNAL

PSEN

INST

ADDR

11 OSC. PERIODS

INST INST INST

ADDR ADDR ADDR

19 OSC. PERIODS

Figure 22. Reset Timing

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INST

ADDR

MC004-1D

11/19/98

IS80C52

OSC

CLOCK

GEN

XTAL 2 XTAL 1

IDL

CPU

INTERRUPT, SERIAL PORT, TIMER BLOCKS

IS80C32

Power-Saving Modes of Operation

The IS80C52/32 has two power-reducing modes. Idle and Power-down. The input through which backup power is supplied during these operations is Vcc. Figure 23 shows the internal circuitry which implements these features. In the Idle mode (IDL = 1), the oscillator continues to run and the Interrupt, Serial Port, and Timer blocks continue to be clocked, but the clock signal is gated off to the CPU. In Power-down (PD = 1), the oscillator is frozen. The Idle and Power-down modes are activated by setting bits in Special Function Register PCON.

Idle Mode

An instruction that sets PCON.0 is the last instruction executed before the Idle mode begins. In the Idle mode, the internal clock signal is gated off to the CPU, but not to the Interrupt, Timer, and Serial Port functions. The CPU status is preserved in its entirety: the Stack Pointer, Program Counter, Program Status Word, Accumulator, and all other registers maintain their data during Idle. The port pins hold the logical states they had at the time Idle was activated. ALE and PSEN hold at logic high levels.

There are two ways to terminate the Idle. Activation of any enabled interrupt will cause PCON.0 to be cleared by hardware, terminating the Idle mode. The interrupt will be serviced, and following RETI the next instruction to be executed will be the one following the instruction that put the device into Idle.

The flag bits GF0 and GF1 can be used to indicate whether an interrupt occurred during normal operation or during an Idle. For example, an instruction that activates Idle can also set one or both flag bits. When Idle is terminated by an interrupt, the interrupt service routine can examine the flag bits.

The other way of terminating the Idle mode is with a hardware reset. Since the clock oscillator is still running, the hardware reset must be held active for only two machine cycles (24 oscillator periods) to complete the reset.

ISSI

Figure 23. Idle and Power-Down Hardware

Power-down Mode

An instruction that sets PCON.1 is the last instruction executed before Power-down mode begins. In the Powerdown mode, the on-chip oscillator stops. With the clock frozen, all functions are stopped, but the on-chip RAM and Special function Registers are held. The port pins output the values held by their respective SFRs. ALE and output lows.

In the Power-down mode of operation, Vcc can be reduced to as low as 2V. However, Vcc must not be reduced before the Power-down mode is invoked, and Vcc must be restored to its normal operating level before the Power-down mode is terminated. The reset that terminates Power-down also frees the oscillator. The reset should not be activated before Vcc is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize (normally less than 10 msec).

The only exit from power-down is a hardware reset. Reset redefines all the SFRs but does not change the on-chip RAM.

PSEN

The signal at the RST pin clears the IDL bit directly and asynchronously. At this time, the CPU resumes program execution from where it left off; that is, at the instruction following the one that invoked the Idle Mode. As shown in Figure 22, two or three machine cycles of program execution may take place before the internal reset algorithm takes control. On-chip hardware inhibits access to the internal RAM during his time, but access to the port pins is not inhibited. To eliminate the possibility of unexpected outputs at the port pins, the instruction following the one that invokes Idle should not write to a port pin or to external data RAM.

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Table 12. Status of the External Pins During Idle and Power-down Modes.

ISSI

Mode Memory ALE

PSENPSEN

PSEN

PSENPSEN

PORT 0 PORT 1 PORT 2 PORT 3

Idle Internal 1 1 Data Data Data Data

Idle External 1 1 Float Data Address Data Power-down Internal 0 0 Data Data Data Data Power-down External 0 0 Float Data Data Data

On-Chip Oscillators

The on-chip oscillator circuitry of the IS80C52/32 is a single stage linear inverter, intended for use as a crystalcontrolled, positive reactance oscillator (Figure 24). In this application the crystal is operated in its fundamental response mode as an inductive reactance in parallel resonance with capacitance external to the crystal (Figure

24). Examples of how to drive the clock with external oscillator are shown in Figure 25.

The crystal specifications and capacitance values (C1 and C2 in Figure 24) are not critical. 20 pF to 30 pF can be used in these positions at a12 MHz to 24 MHz frequency with good quality crystals. (For ranges greater than 24 MHz refer to Figure 26.) A ceramic resonator can be used in place of the crystal in cost-sensitive applications. When a ceramic resonator is used, C1 and C2 are normally selected to be of somewhat higher values. The manufacturer of the ceramic resonator should be consulted for recommendation on the values of these capacitors.

Figure 24. Oscillator Connections

XTAL2

XTAL1

GND

EXTERNAL

OSCILLATOR

SIGNAL

XTAL2

XTAL1

GND

Figure 25. External Clock Drive Configuration

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XTAL2 XTAL1

Figure 26. For High Speed (> 24 MHz)

Note:

When the frequency is higher than 24 MHz, please refer to Table 13 for recommended value of C1, C2, and R.

Table 13. Recommended Value for C1, C2, R

Frequency Range

3.5 MHz-24 MHz 30 MHz-40 MHz

C1 20 pF-30 pF 3 pF-10 pF C2 20 pF-30 pF 3 pF-10 pF R Not Apply 6.2K-10K

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ROM Verification

The address of the program memory location to be read is applied to Port 1 and pins P2.4-P2.0. The other pins should be held at the “Verify” level are indicated in Figure

26. The contents of the addressed locations exits on Port

0. External pullups are required on Port 0 for this operation. Figure 26 shows the setup to verify the program memory.

ISSI

+ 5V

4-6 MHz

A7-A0

A12-A8

1 1 1 0 0 0

P2.4-P2.0

RST EA ALE PSEN P2.7 P2.6

XTAL1

XTAL2 GND

Figure 27. ROM Verification

Vcc

10K x 8

PGM DATA

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ROM Lock System

The program lock system, when programmed, protects the ROM code against software piracy. The IS80C52/32 has a two-level program lock system (see Table 14) and a 32-byte encryption table. No matter what lock bit is, the user submits the encryption table with his or her code in verify ROM mode. Both the lock-bit and encryption array

Table 14. Program Lock Bits

LB1 LB2 Protection Type

1 U U No Program Lock Features enabled. (Code verify will still be

encrypted by the Encryption Array if Programmed)

2 P U MOVC instructions executed from external program memory

are diabled form fetching code bytes from internal memory, EA is sampled and latched on Reset.

3 P P Same as 2, also ROM verify is disabled.

Encryption Array

Within the ROM array are 32 bytes of Encryption Array that are initially unprogrammed (all 1's). Every time that a byte is addressed during verify, five address lines are used to select a byte of the Encryption Array.This byte is then exclusive-NOR'ed (XNOR) with the code byte, creating an Encryption verify byte. The algorithm, with the array in the unprogrammed state (all 1's), will return the code in its original, unmodified form.

When using the encryption array, one important factor needs to be considered. If a code byte has the value 0FFH, verifying the byte will produce the encryption byte value. If a large block (> 32 bytes) of code is left unprogrammed, a verification routine will display the contents of the encryption array. For this reason, all unused code bytes should be programmed with some value other than 0FFH, and not all of them the same value.

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ABSOLUTE MAXIMUM RATINGS

(1)

Symbol Parameter Value Unit

VTERM Terminal Voltage with Respect to GND TBIAS Temperature Under Bias

(3)

(2)

–2.0 to +7.0 V

–40 to +85 °C TSTG Storage Temperature –65 to +125 °C PT Power Dissipation 1.5 W

Note:

1. Stress greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.

2. Minimum DC input voltage is –0.5V. During transitions, inputs may undershoot to –2.0V for periods less than 20 ns. Maximum DC voltage on output pins is Vcc + 0.5V which may overshoot to Vcc + 2.0V for periods less than 20 ns.

3. Operating temperature is for commercial products only defined by this specification.

OPERATING RANGE

(1)

Range Ambient Temperature VCC Oscillator Frequency

Commercial 0°C to +70°C 5V ± 10% 3.5 to 40 MHz Industrial –40°C to +85°C 5V ± 10% 3.5 to 40 MHz

Note:

1. Operating ranges define those limits between which the functionality of the device is guaranteed.

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DC CHARACTERISTICS

(TA = 0°C to 70°C; Vcc = 3.3V ± 10%; GND = 0V)

Symbol Parameter Test conditions Min Max Unit

VIL Input low voltage (All except EA) –0.5 0.2Vcc – 0.1 V

VIL1 Input low voltage (EA) –0.5 0.2Vcc – 0.3 V

VIH Input high voltage 0.2Vcc + 0.9 Vcc + 0.5 V

(All except XTAL 1, RST)

VIH1 Input high voltage (XTAL 1) 0.7Vcc Vcc + 0.5 V

VSCH+ RST positive schmitt-trigger 0.7Vcc Vcc + 0.5 V

threshold voltage

VSCH– RST negative schmitt-trigger 0 0.2Vcc V

threshold voltage

(1)

Vol

VOL1

(1)

Output low voltage Iol = 100 µA — 0.3 V (Ports 1, 2, 3) IOL = 1.6 mA — 0.45 V

IOL = 3.5 mA — 1.0 V Output low voltage IOL = 200 µA — 0.3 V (Port 0, ALE,

PSEN

)IOL = 3.2 mA — 0.45 V

ISSI

IOL = 7.0 mA — 1.0 V

VOH Output high voltage IOH = –10 µA 0.9Vcc — V

(Ports 1, 2, 3, ALE,

PSEN

) Vcc = 4.5V-5.5V

IOL = –25 µA 0.75Vcc — V

IOL = –60 µA 2.4 — V

VOH1 Output high voltage IOH = –80 µA 0.9Vcc — V

(Port 0, ALE,

PSEN

) Vcc = 4.5V-5.5V

IOH = –300 µA 0.75Vcc — V

IOH = –800 µA 2.4 — V

IIL Logical 0 input current (Ports 1, 2, 3) VIN = 0.45V — –110 µA ILI Input leakage current (Port 0) 0.45V < VIN < Vcc –10 10 µA

ITL Logical 1-to-0 transition current VIN = 2.0V — –650 µA

(Ports 1, 2, 3)

RRST RST pulldown resister 50 300 KΩ

Note:

1. Under steady state (non-transient) conditions, Iol must be externally limited as follows: Maximum I Maximum IOL per 8-bit port

Maximum total I

OL exceeds the test condition, VOL may exceed the related specification.

If I

OL per port pin: 10 mA

Port 0: 26 mA Ports 1, 2, 3: 15 mA

OL for all output pins: 71 mA

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POWER SUPPLY CHARACTERISTICS

Symbol Parameter Test conditions Min Max Unit

Icc Power supply current

Active mode 12 MHz — 20 mA

Idle mode 12 MHz — 5 mA

Power-down mode VCC = 5V — 50 µA

Note:

1. See Figures 28, 29, 30, and 31 for Icc test conditiions.

(1)

Vcc = 5.0V

16 MHz — 26 mA 20 MHz — 32 mA 24 MHz — 38 mA 32 MHz — 50 mA 40 MHz — 62 mA

16 MHz — 6 mA 20 MHz — 7.6 mA 24 MHz — 9 mA 32 MHz — 12 mA 40 MHz — 15 mA

ISSI

CLOCK

SIGNAL

Vcc

RST Vcc

XTAL2 XTAL1

GND

Icc

Vcc

CLOCK

SIGNAL

RST Vcc

XTAL2 XTAL1

GND

Figure 28. Active Mode Figure 29. Idle Mode

Vcc

Icc

RST Vcc

Vcc

XTAL2 XTAL1

GND

Vcc

Icc

Vcc

Figure 30. Power-down Mode

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AC CHARACTERISTICS

(TA = 0°C to 70°C; Vcc = 3.3V ± 10%; GND = 0V; Cl for Port 0, ALE and PSEN Outputs = 100 pF; Cl for other outputs = 80 pF)

CLCX

Vcc — 0.5V

0.45V

Note:

1. Clock signal waveform for Icc tests in active and idle mode (tCLCH = tCHCL = 5 ns)

0.7Vcc

0.2Vcc — 0.1

CHCL

Figure 31. Icc Test Conditions

CLCL

CHCX

CLCH

EXTERNAL MEMORY CHARACTERISTICS

24 MHz 40 MHz Variable Oscillator

Clock Clock (3.5-24 MHz)

Symbol Parameter Min Max Min Max Min Max Unit

1/tCLCL Oscillator frequency — — — — 3.5 24 MHz tLHLL ALE pulse width 43 — 40 — 2tCLCL–40 — ns tAVLL Address valid to ALE low 2 — 9 — tCLCL–40 — ns tLLAX Address hold after ALE low 7 — 30 — tCLCL–35 — ns tLLIV ALE low to valid instr in — 105 — 70 — 3tCLCL–20 ns tLLPL ALE low to tPLPH tPLIV tPXIX Input instr hold after tPXIZ Input instr float after tAVIV Address to valid instr in — 147 — 80 — 4tCLCL–20 ns tPLAZ tRLRH tWLWH WR pulse width 150 — 100 — 6tCLCL–100 — ns tRLDV tRHDX Data hold after tRHDZ Data float after tLLDV ALE low to valid data in — 244 — 150 — 8tCLCL–90 ns tAVDV Address to valid data in — 285 — 180 — 9tCLCL–90 ns tLLWL ALE low to RD or WR low 75 175 60 95 3tCLCL–50 3tCLCL+50 ns tAVWL Address to RD or WR low 77 — 65 — 4tCLCL–90 — ns tQVWX Data valid to WR transition 2 — 10 — tCLCL–40 — ns tWHQX Data hold after tQVWH Data valid to WR high 219 — 165 — 7tCLCL–70 — ns tRLAZ tWHLH

PSEN PSEN

PSEN RD

pulse width 150 — 100 — 6tCLCL–100 — ns

low to valid data in — 114 — 90 — 5tCLCL–95 ns

low to address float — 63 — 0 — 2tCLCL–20 ns

or WR high to ALE high 2 82 15 35 tCLCL–40 tCLCL+40 ns

PSEN

low 2 — 15 — tCLCL–40 — ns pulse width 80 — 65 — 3tCLCL–45 — ns low to valid instr in — 73 — 45 — 2tCLCL–10 ns

PSEN PSEN

low to address float — 10 — 5 — 10 ns

RD RD

0— 0— 0 — ns

—73 —25 — 2tCLCL–10 ns

0— 0— 0 — ns

—63 —50 — 2tCLCL–70 ns

2— 10— tCLCL–40 — ns

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EXTERNAL MEMORY CHARACTERISTICS

(Continued)

24 MHz 40 MHz Variable Oscillator

Clock Clock (3.5-24 MHz)

Symbol Parameter Min Max Min Max Min Max Unit

tXLXL Serial port clock cycle time 500 — 250 — 12tCLCL–10 — ns tQVXH Output data setup to 284 — 170 — 10tCLCL–133 — ns

clock rising edge

tXHQX Output data hold after 33 — 33 — 2tCLCL–50 — ns

clock rising edge

tXHDX Input data hold after 0 — 0 — 0 — ns

clock rising edge

tXHDV Clock rising edge to — 284 — 117 — 10tCLCL–133 ns

input data valid

EXTERNAL CLOCK DRIVE

ISSI

Symbol wParameter Min Max Unit

1/tCLCL Oscillator Frequency 3.5 40 MHz tCHCX High time 10 — ns tCLCX Low time 10 — ns tCLCH Rise time — 10 ns tCHCL Fall time — 10 ns

ROM VERIFICATION CHARACTERISTICS

Symbol Parameter Min Max Unit

1/tCLCL Oscillator Frequency 2.5 40 MHz tAVQV Address to data valid — 48tCLCL tELQV ENABLE low to data valid — 48tCLCL tEHQZ Data float after ENABLE 0 48tCLCL

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TIMING WAVEFORMS

ALE

PSEN

AVLL

LHLL

LLPL

LLAX

PLAZ

PLPH

PLIV

PXIX

PXIZ

ISSI

PORT 0

PORT 2

ALE

PSEN

PORT 0

A7-A0 INSTR IN A7-A0

LLIV

AVIV

A15-A8 A15-A8

Figure 32. External Program Memory Read Cycle

WHLH

LLDV

LLWL

AVLL

A7-A0 FROM RI OR DPL INSTR INA7-A0 FROM PCL

LLAX

RLAZ

RLDV

RLRH

RHDX

DATA IN

RHDZ

AVWL

AVDV

PORT 2

Figure 33. External Data Memory Read Cycle

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A15-A8 FROM DPH A15-A8 FROM PCH

IS80C52 IS80C32

ALE

PSEN

LLWL

WLWH

WHLH

ISSI

PORT 0

PORT 2

INSTRUCTION

ALE

CLOCK

OUT

DATA

DATAIN

AVLL

LLAX

A7-A0 FROM RI OR DPL INSTR INA7-A0 FROM PCL

AVWL

A15-A8 FROM DPH A15-A8 FROM PCH

Figure 34. External Data Memory Write Cycle

XLXL

QVXH

XHDV

VALID VALID VALID VALID VALID VALID VALID VALID

XHQX

XHDX

QVWX

DATA OUT

WHQX

786543210

76543210

SET TI

SET RI

Figure 35. Shift Register Mode Timing Waveform

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Vcc – 0.5V

0.45V

P1.0-P1.7 P2.0-P2.3

PORT 0

P2.7

Figure 36. External Clock Drive Waveform

0.7Vcc

0.2Vcc – 0.1

Figure 37. ROM Verification Waveforms

ELQV

CHCL

ADDRESS

AVQV

DATA OUT

CLCX

CLCL

EHQZ

CHCX

CLCH

Vcc - 0.5V

0.2Vcc + 0.9V

0.45V

Figure 38. AC Test Point

Note:

1. AC inputs during testing are driven at VCC – 0.5V for logic “1” and 0.45V for logic “0”. Timing measurements are made at V

IH min for logic “1” and max for logic “0”.

0.2Vcc - 0.1V

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ORDERING INFORMATION COMMERCIAL TEMPERATURE:

0°C to +70°C

Speed Order Part Number Package

12 MHz IS80C52-12PL PLCC

IS80C52-12PQ PQFP IS80C52-12W 600-mil Plastic DIP

24 MHz IS80C52-24PL PLCC

IS80C52-24PQ PQFP IS80C52-24W 600-mil Plastic DIP

40 MHz IS80C52-40PL PLCC

IS80C52-40PQ PQFP IS80C52-40W 600-mil Plastic DIP

12 MHz IS80C32-12PL PLCC

IS80C32-12PQ PQFP IS80C32-12W 600-mil Plastic DIP

24 MHz IS80C32-24PL PLCC

IS80C32-24PQ PQFP IS80C32-24W 600-mil Plastic DIP

40 MHz IS80C32-40PL PLCC

IS80C32-40PQ PQFP IS80C32-40W 600-mil Plastic DIP

ORDERING INFORMATION INDUSTRIAL TEMPERATURE:

–40°C to +85°C

Speed Order Part Number Package

12 MHz IS80C52-12PLI PLCC

IS80C52-12PQI PQFP IS80C52-12WI 600-mil Plastic DIP

24 MHz IS80C52-24PLI PLCC

IS80C52-24PQI PQFP IS80C52-24WI 600-mil Plastic DIP

40 MHz IS80C52-40PLI PLCC

IS80C52-40PQI PQFP IS80C52-40WI 600-mil Plastic DIP

12 MHz IS80C32-12PLI PLCC

IS80C32-12PQI PQFP IS80C32-12WI 600-mil Plastic DIP

24 MHz IS80C32-24PLI PLCC

IS80C32-24PQI PQFP IS80C32-24WI 600-mil Plastic DIP

40 MHz IS80C32-40PLI PLCC

IS80C32-40PQI PQFP IS80C32-40WI 600-mil Plastic DIP

ISSI

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2231 Lawson Lane

Santa Clara, CA 95054

Fax: (408) 588-0806

Toll Free: 1-800-379-4774

http://www.issiusa.com

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Datasheet IS80C52-12PL, IS80C52-40WI, IS80C52-40W, IS80C52-40PQI, IS80C52-40PQ Datasheet (ISSI)

Specifications and Main Features

Frequently Asked Questions

User Manual