IC80C51 IC80C31 IC80C51 IC80C31 CMOS SINGLE CHIP 8-BIT MICROCONTROLLER FEATURES GENERAL DESCRIPTION • • • • • • • • The ICSI IC80C51 and IC80C31 are high-performance microcontroller fabricated using high-density CMOS technology. The CMOS IC80C51/31 is functionally compatible with the industry standard 80C51/31 microcontrollers. • • • • • • • 80C51 based architecture 4K x 8 ROM (IC80C51 only) 128 x 8 RAM Two 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 Six interrupt sources Most instructions execute in 0.3 µs CMOS and TTL compatible Maximum speed: 40 MHz @ Vcc = 5V Packages available: – 40-pin DIP – 44-pin PLCC – 44-pin PQFP The IC80C51/31 is designed with 4K x 8 ROM (IC80C51 only); 128 x 8 RAM; 32 programmable I/O lines; a serial I/ O port for either multiprocessor communications, I/O expansion or full duplex UART; two 16-bit timer/counters; an six-source, two-priority-level, nested interrupt structure; and an on-chip oscillator and clock circuit. The IC80C51/31 can be expanded using standard TTL compatible memory. P1.0 1 40 VCC P1.1 2 39 P0.0/AD0 P1.2 3 38 P0.1/AD1 P1.3 4 37 P0.2/AD2 P1.4 5 36 P0.3/AD3 P1.5 6 35 P0.4/AD4 P1.6 7 34 P0.5/AD5 P1.7 8 33 P0.6/AD6 RST 9 32 P0.7/AD7 RxD/P3.0 10 31 EA TxD/P3.1 11 30 ALE INT0/P3.2 12 29 PSEN INT1/P3.3 13 28 P2.7/A15 T0/P3.4 14 27 P2.6/A14 T1/P3.5 15 26 P2.5/A13 WR/P3.6 16 25 P2.4/A12 RD/P3.7 17 24 P2.3/A11 XTAL2 18 23 P2.2/A10 XTAL1 19 22 P2.1/A9 GND 20 21 P2.0/A8 Figure 1. IC80C51/31 Pin Configuration: 40-pin DIP ICSI 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 2000, Integrated Circuit Solution Inc. Integrated Circuit Solution Inc. MC001-0B 1 P1.3 P1.2 P1.1 P1.0 NC VCC P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 INDEX P1.4 IC80C51 IC80C31 6 5 4 3 2 1 44 43 42 41 40 P1.5 7 39 P0.4/AD4 P1.6 8 38 P0.5/AD5 P1.7 9 37 P0.6/AD6 RST 10 36 P0.7/AD7 RxD/P3.0 11 35 EA NC 12 34 NC TxD/P3.1 13 33 ALE INT0/P3.2 14 32 PSEN INT1/P3.3 15 31 P2.7/A15 T0/P3.4 16 30 P2.6/A14 T1/P3.5 17 29 P2.5/A13 18 19 20 21 22 23 24 25 26 27 28 WR/P3.6 RD/P3.7 XTAL2 XTAL1 GND NC A8/P2.0 A9/P2.1 A10/P2.2 A11/P2.3 A12/P2.4 TOP VIEW Figure 2. IC80C5/31 Pin Configuration: 44-pin PLCC S3-2 Integrated Circuit Solution Inc. MC001-0B P1.4 P1.3 P1.2 P1.1 P1.0 NC VCC P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 IC80C51 IC80C31 44 43 42 41 40 39 38 37 36 35 34 P0.6/AD6 RST 4 30 P0.7/AD7 RxD/P3.0 5 29 EA NC 6 28 NC TxD/P3.1 7 27 ALE INT0/P3.2 8 26 PSEN INT1/P3.3 9 25 P2.7/A15 T0/P3.4 10 24 P2.6/A14 T1/P3.5 11 23 P2.5/A13 12 13 14 15 16 17 18 19 20 21 22 A12/P2.4 31 A11/P2.3 3 A10/P2.2 P1.7 A9/P2.1 P0.5/AD5 A8/P2.0 32 NC 2 GND P1.6 XTAL1 P0.4/AD4 XTAL2 33 RD/P3.7 1 WR/P3.6 P1.5 Figure 3. IC80C51/31 Pin Configuration: 44-pin PQFP Integrated Circuit Solution Inc. MC001-0B 3 IC80C51 IC80C31 VCC ADDRESS DECODER & 128 BYTES RAM RAM ADDR REGISTER P2.0-P2.7 P0.0-P0.7 P2 DRIVERS P0 DRIVERS P2 LATCH STACK POINT B REGISTER PCON SCON TH0 ADDRESS DECODER & 4K ROM P0 LATCH PROGRAM ADDRESS REGISTER ACC TMOD TCON TL0 TH1 TMP2 TMP1 PROGRAM COUNTER TL1 SBUF IE IP INTERRUPT BLOCK SERIAL PORT BLOCK TIMER BLOCK PC INCREMENTER ALU PSW PSEN ALE RST TIMING AND CONTROL EA INSTRUCTION REGISTER BUFFER DPTR P3 LATCH P1 LATCH P3 DRIVERS P1 DRIVERS P3.0-P3.7 P1.0-P1.7 OSCILLATOR XTAL1 XTAL2 Figure 4. IC80C51/31 Block Diagram S3-4 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 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 access 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. EA 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 internal ROM seze. 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 0 pins that have 1s written to them float and can be used as highimpedance inputs. Port 0 is also the multiplexed low-order address and data bus during accesses to external program and data memory. In this application, it uses strong internal pullups when emitting 1s. P1.0-P1.7 1-8 2-9 40-44 1-3 I/O Port 1: Port 1 is an 8-bit bidirectional I/O port with internal 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. 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 Registers. Integrated Circuit Solution Inc. MC001-0B 5 IC80C51 IC80C31 Table 1. Detailed Pin Description (continued) 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 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 IC80C51/31, as listed below: 10 11 12 13 14 15 16 17 11 13 14 15 16 17 18 19 5 7 8 9 10 11 12 13 I O I I I I O O RxD (P3.0): Serial input port. TxD (P3.1): Serial output port. INT0 (P3.2): External interrupt 0. INT1 (P3.3): External interrupt 1. T0 (P3.4): Timer 0 external input. T1 (P3.5): Timer 1 external input. WR (P3.6): External data memory write strobe. RD (P3.7): External data memory read strobe. PSEN 29 32 26 O Program Store Enable: The read strobe to external program memory. When the device is executing code from the external program memory, PSEN is activated twice each machine cycle except that two PSEN activations are skipped during each access to external data memory. PSEN is not activated during fetches from internal program memory. 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. S3-6 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 OPERATING DESCRIPTION The detail description of the IC80C51 included in this description are: addressing. Figure 6 shows internal data memory organization and SFR Memory Map. • Memory Map and Registers The lower 128 bytes of RAM can be divided into three segments as listed below and shown in Figure 7. • Timer/Counters 1. Register Banks 0-3: 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. • Serial Interface • Interrupt System • Other Information MEMORY MAP AND REGISTERS Memory The IC80C51/31 has separate address spaces for program and data memory. The program and data memory can be up to 64K bytes long. The lower 4K program memory can reside on-chip.(IC80C51 only) Figure 5 shows a map of the IC80C51/31 program and data memory. The IC80C51/31 has 128 bytes of on-chip RAM, plus numbers of special function registers. The 128 bytes can be accessed either by direct addressing or by indirect 2. 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. 3. 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. Program Memory (Read Only) Data Memory (Read/Write) FFFFH FFFFH: 64K External External Internal 0FFFH: 4K EA = 1 Internal EA = 0 External 0000 PSEN FFH 7FH 00 80H 0000 RD WR Figure 5. IC80C51/31 Program and Data Memory Structure Integrated Circuit Solution Inc. MC001-0B 7 IC80C51 IC80C31 SPECIAL FUNCTION REGISTERS 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. 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. The functions of the SFRs are outlined in the following sections, and detailed in Table 2. FFH Not Available in IC80C51/31 Upper 128 Accessible by Direct Addressing 80H 7FH 80H Accessible by Direct and Indirect Addressing Lower 128 Special Function Registers 0 Ports, Status and Control Bits, Timer, Registers, Stack Pointer, Accumulator (Etc.) F8 F0 E8 E0 D8 D0 C8 C0 B8 B0 A8 A0 98 90 88 80 B ACC PSW IP P3 IE P2 SCON P1 TCON P0 SBUF TMOD SP TL0 DPL TL1 DPH TH0 TH1 PCON FF F7 EF E7 DF D7 CF C7 BF B7 AF A7 9F 97 8F 87 Bit Addressable Figure 6. Internal Data Memory and SFR Memory Map 8 BYTES 78 7F 70 77 68 6F 60 67 58 5F 50 57 48 4F 40 47 38 3F 30 37 ...7F 28 20 SCRATCH PAD AREA 0 ... 2F 27 18 BANK3 1F 10 BANK2 17 08 BANK 1 0F 00 BANK 0 07 BIT ADDRESSABLE SEGMENT REGISTER BANKS Figure 7. Lower 128 Bytes of Internal RAM S3-8 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 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 onchip 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. initiates the transmission.) When data is moved from SBUF, it comes from the receive buffer. Timer Registers Register pairs (TH0, TL0) and (TH1, TL1),are the 16-bit Counter registers for Timer/Counters 0,1 and 2, respectively. 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. Ports 0 To 3 P0, P1, P2, and P3 are the SFR latches of Ports 0, 1, 2, and 3, respectively. 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 Integrated Circuit Solution Inc. MC001-0B 9 IC80C51 IC80C31 Table 2. Special Function Registers Symbol Description Direct Address ACC(1) Bit Address, Symbol, or Alternative Port Function Reset Value Accumulator E0H E7 E6 E5 E4 E3 E2 E1 E0 00H B(1) DPH DPL B register Data pointer (DPTR) high Data pointer (DPTR) low F0H 83H 82H F7 F6 F5 F4 F3 F2 F1 F0 00H 00H 00H IE(1) Interrupt enable A8H IP(1) Interrupt priority B8H P0(1) Port 0 80H P1(1) Port 1 90H P2(1) Port 2 A0H P3(1) Port 3 B0H PCON Power control 87H PSW(1) SBUF Program status word Serial data buffer D0H 99H AF EA BF — 87 P0.7 AD7 97 P1.7 — A7 P2.7 AD15 B7 P3.7 RD SMOD D7 CY AE — BE — 86 P0.6 AD6 96 P1.6 — A6 P2.6 AD14 B6 P3.6 WR — D6 AC AD — BD — 85 P0.5 AD5 95 P1.5 — A5 P2.5 AD13 B5 P3.5 T1 — D5 F0 AC ES BC PS 84 P0.4 AD4 94 P1.4 — A4 P2.4 AD12 B4 P3.4 T0 — D4 RS1 AB ET1 BB PT1 83 P0.3 AD3 93 P1.3 — A3 P2.3 AD11 B3 P3.3 INT1 GF1 D3 RS0 AA EX1 BA PX1 82 P0.2 AD2 92 P1.2 — A2 P2.2 AD10 B2 P3.2 INT0 GF0 D2 OV A9 ET0 B9 PT0 81 P0.1 AD1 91 P1.1 — A1 P2.1 AD9 B1 P3.1 TXD PD D1 — A8 EX0 B8 PX0 80 P0.0 AD0 90 P1.0 — A0 P2.0 AD8 B0 P3.0 RXD IDL D0 P SCON(1) SP Serial controller Stack pointer 98H 81H 9F SM0 9E SM1 9D SM2 9C REN 9B TB8 9A RB8 99 TI 98 RI TCON(1) TMOD TH0 TH1 TL0 TL1 Timer control Timer mode Timer high 0 Timer high 1 Timer low 0 Timer low 1 88H 89H 8CH 8DH 8AH 8BH 8F 8E TF1 TR1 GATE C/T 8D TF0 M1 8C 8B TR0 IE1 M0 GATE 8A IT1 C/T 89 IE0 M1 88 IT0 M0 0XX00000B XXX00000B FFH FFH FFH FFH 0XXX0000B 00H XXXXXXXXB 00H 07H 00H 00H 00H 00H 00H 00H Notes: 1. Denotes bit addressable. S3-10 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 1. User software should not write 1s to reserved bits. These bits may be used in future products to invoke new features. The detail description of each bit is as follows: PSW: IE: Program Status Word. Bit Addressable. 7 CY 6 AC 5 F0 4 RS1 3 RS0 2 OV 1 — 0 P Register Description: 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.(1) RS0 PSW.3 Register bank selector bit 0.(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 Power Control Register. Not Bit Addressable. 5 — 4 — 3 GF1 2 GF0 1 PD 7 EA 6 — 5 — 4 ES 3 ET1 2 EX1 1 0 ET0 EX0 Register Description: 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 use. (5) — IE.5 Not implemented, reserve for future use. (5) ES ET1 IE.4 IE.3 EX1 ET0 IE.2 IE.1 EX0 IE.0 Enable or disable the serial port interrupt. Enable or disable the Timer 1 overflow interrupt. Enable or disable External Interrupt 1. Enable or disable the Timer 0 overflow interrupt. 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). PCON: 7 6 SMOD — Interrupt Enable Register. Bit Addressable. 0 IDL Register Description: 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.(1) — Not implemented, reserve for future use.(1) — Not implemented, reserve for future use.(1) GF1 General purpose flag bit. GF0 General purpose flag bit. PD Power-down bit. Setting this bit activates powerdown mode. IDL Idle mode bit. Setting this bit activates idle mode. operation in the IC80C51/31. If 1s are written to PD and IDL at the same time, PD takes precedence. Interrupt Source IE0 TF0 IE1 TF1 RI & TI Vector Address 0003H 000BH 0013H 001BH 0023H 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. Note: Integrated Circuit Solution Inc. MC001-0B 11 IC80C51 IC80C31 IP: TCON: Interrupt Priority Register. Bit Addressable. Timer/Counter Control Register. Bit Addressable 7 — 6 — 5 — 4 PS 3 PT1 2 PX1 1 0 PT0 PX0 Register Description: — IP.7 Not implemented, reserve for future use (3) — IP.6 Not implemented, reserve for future use (3) — IP.5 Not implemented, reserve for future use (3) PS PT1 IP.4 IP.3 Defines Serial Port interrupt priority level Defines Timer 1 interrupt priority level PX1 PT0 PX0 IP.2 IP.1 IP.0 Defines External Interrupt 1 priority level Defines Timer 0 interrupt priority level 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 3. User software should not write 1s to reserved bits. These bits may be used in future products to invoke new features. S3-12 7 TF1 6 TR1 5 TF0 4 TR0 3 IE1 2 IT1 1 IE0 0 IT0 Register Description: 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. Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 TMOD: SCON: Timer/Counter Mode Control Register. Not Bit Addressable. Serial Port Control Register. Bit Addressable. Timer 1 T M1 M0 GATE C/T GATE Timer 0 T M1 M0 C/T 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). C/T 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.(1) Mode selector bit.(1) M0 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). 7 6 5 SM0 SM1 SM2 4 REN 3 TB8 2 RB8 1 TI 0 RI Register Description: SM0 SCON.7 Serial port mode specifier.(1) SM1 SCON.6 Serial port mode specifier.(1) SM2 SCON.5 Enable the multiprocessor communication 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 eighth 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 eighth 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 : UART Operating Modes SM0 SM1 MODE Integrated Circuit Solution Inc. MC001-0B 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 13 IC80C51 IC80C31 TIMER/COUNTERS Timer 0 and Timer 1 The IC80C51/31 has two 16-bit Timer/Counter registers: Timer 0,Timer 1. All two can be configured to operate either as Timers or event Counters. Timer/Counters 0 and 1 are present in both the IC80C51/ 31 and IC80C52/32.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. 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 and T1. 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. 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 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. 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. 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 INT1 = 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. 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). ONE MACHINE ONE MACHINE CYCLE CYCLE S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 OSC (XTAL2) OSC DIVIDE 12 C/T = 0 TL1 (5 BITS) TH1 (8 BITS) TF1 INTERRUPT C/T = 1 T1 PIN CONTROL TR1 GATE INT1 PIN Figure 8. Timer/Counter 1 Mode 0: 13-Bit Counter S3-14 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 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 9. 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 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 11. 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 IC80C51 can appear to have three Timer/Counters. 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. DIVIDE 12 C/T = 0 TL1 (8 BITS) TF1 INTERRUPT C/T = 1 T1 PIN RELOAD CONTROL TR1 GATE TH1 (8 BITS) INT0 PIN Figure 9. Timer/Counter 1 Mode 2: 8-Bit Auto-Reload Integrated Circuit Solution Inc. MC001-0B 15 IC80C51 IC80C31 OSC DIVIDE 12 1/12 FOSC 1/12 FOSC C/T = 0 TL0 (8 BITS) TF0 INTERRUPT TH0 (8 BITS) TF1 INTERRUPT C/T = 1 T0 PIN CONTROL TR0 GATE INT0 PIN 1/12 FOSC TR1 CONTROL Figure 10. Timer/Counter 0 Mode 3: Two 8-Bit Counters S3-16 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 Timer Setup Table 5. Timer/Counter 1 Used as a Timer 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 Mode Timer 0 Function TMOD Internal External Control(1) Control(2) 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 TMOD Internal External Control(1) Control(2) Mode Timer 1 Function 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 Internal External Control(1) Control(2) Mode Timer 1 Function 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 Internal External Control(1) Control(2) Mode Timer 0 Function 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. 2. The Timer is turned ON/OFF by the 1-to-0 transition on INT0 (P3.2) when TR0=1 (hardware control) Integrated Circuit Solution Inc. MC001-0B 17 IC80C51 IC80C31 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 11). 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 12). 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 13). 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 14). 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. S3-18 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. Oscillator Frequency 12 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 0 Baud Rate = SMOD Mode 2 Baud Rate = 2 64 x (Oscillator Frequency) In the IC80C51/31, the Timer 1 overflow rate da termines th e baud rates in Modes 1 and 3. Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 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 = Baud Rate 2SMOD 32 X (Timer 1 Overflow 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 three 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 = Baud Rate 2SMOD 32 X Oscillator Frequency 12x [256 – (TH1)] 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. 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 Table 7. Commonly Used Baud Rates Generated by Timer 1 Timer 1 Baud Rate Mode 0 Max: 1 MHz Mode 2 Max: 375K Modes 1, 3: 62.5K 19.2K 9.6K 4.8K 2.4K 1.2K 137.5 110 110 fOSC 12 MHz 12 MHz 12 MHz 11.059 MHz 11.059 MHz 11.059 MHz 11.059 MHz 11.059 MHz 11.986 MHz 6 MHz 12 MHz Integrated Circuit Solution Inc. MC001-0B SMOD X 1 1 1 0 0 0 0 0 0 0 C/T T X X 0 0 0 0 0 0 0 0 0 Mode X X 2 2 2 2 2 2 2 2 1 Reload Value X X FFH FDH FDH FAH F4H E8H 1DH 72H FEEBH 19 IC80C51 IC80C31 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 tenth 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 IC80C51 the baud rate is determined by the Timer 1 overflow rate. 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 S3-20 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-by16 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. 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-to-0 transition in RXD. More About Modes 2 and 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). 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 Timer 1. 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 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 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-by16 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 eleventh divide-by-16 rollover after "write to SBUF". Table 8. Serial Port Setup Mode SCON 0 10H 1 50H 2 90H 3 D0H 0 NA 1 70H 2 B0H 3 F0H SM2Variation Single Processor Environment (SM2 = 0) Multiprocessor Environment (SM2 = 1) 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 to the input shift register. 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, 1s 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 ninth 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. Integrated Circuit Solution Inc. MC001-0B 21 IC80C51 IC80C31 IC80C51/31 INTERNAL BUS WRITE TO SBUF S D Q CL RXD P3.0 ALT OUTPUT FUNCTION SBUF SHIFT ZERO DETECTOR START SHIFT TX CONTROL S6 TX CLOCK SEND SERIAL PORT INTERRUPT RI RX CLOCK REN RI TXD P3.1 ALT OUTPUT FUNCTION SHIFT CLOCK RECEIVE RX CONTROL SHIFT 1 1 1 1 1 1 1 0 START RXD P3.0 ALT INPUT FUNCTION INPUT SHIFT REG. LOAD SBUF SHIFT SBUF READ SBUF IC80C51/31 INTERNAL BUS 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 ALE WRITE TO SBUF SEND S6P2 SHIFT RXD (DOUT) D0 D1 D2 D3 D5 D4 D6 D7 TRANSMIT TXD (SHIFT CLOCK) S3P1 TI S6P1 WRITE TO SCON (CLEAR RI) RI RECEIVE SHIFT RXD (DIN) RECEIVE D0 D1 D2 D3 D4 D5 D6 D7 S5P2 TXD (SHIFT CLOCK) Figure 11. Serial Port Mode 0 S3-22 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 IC80C51/31 INTERNAL BUS TB8 TIMER 1 OVERFLOW WRITE TO SBUF 2 SMOD =0 S D Q CL SMOD =1 SBUF TXD ZERO DETECTOR SHIFT DATA TX CONTROL SEND RX CLOCK TI START 16 SERIAL PORT INTERRUPT 16 SAMPLE LOAD SBUF SHIFT 1FFH RI RX CLOCK 1-TO-0 TRANSITION DETECTOR RX CONTROL START BIT DETECTOR INPUT SHIFT REG. (9 BITS) RXD LOAD SBUF SHIFT SBUF READ SBUF IC80C51/31 INTERNAL BUS TX CLOCK WRITE TO SBUF SEND S1P1 DATA TRANSMIT SHIFT START BIT TXD D0 D1 D2 D3 D4 D5 D6 STOP BIT D7 TI RX CLOCK RXD RECEIVE 16 RESET START BIT D0 D1 D2 D3 D4 D5 D6 D7 STOP BIT BIT DETECTOR SAMPLE TIMES SHIFT RI Figure 12. Serial Port Mode 1 Integrated Circuit Solution Inc. MC001-0B 23 IC80C51 IC80C31 IC80C51/31 INTERNAL BUS TB8 WRITE TO SBUF S D Q CL SBUF TXD ZERO DETECTOR PHASE 2 CLOCK (1/2 fOSC) START STOP BIT GEN SHIFT DATA TX CONTROL TX CLOCK SEND TI MODE 2 16 SMOD 1 2 SERIAL PORT INTERRUPT SMOD 0 16 (SMOD IS PCON. 7) SAMPLE 1-TO-0 TRANSITION DETECTOR START LOAD SBUF SHIFT 1FFH RI RX CLOCK RX CONTROL BIT DETECTOR INPUT SHIFT REG. (9 BITS) RXD LOAD SBUF SHIFT SBUF READ SBUF IC80C51/31 INTERNAL BUS TX CLOCK WRITE TO SBUF SEND S1P1 DATA TRANSMIT SHIFT START BIT TXD D0 D1 D2 D3 D4 D5 D6 D2 D3 D4 D7 TB8 STOP BIT D6 D7 TI STOP BIT GEN RX CLOCK RXD RECEIVE 16 RESET START BIT D0 D1 D5 RB8 STOP BIT BIT DETECTOR SAMPLE TIMES SHIFT RI Figure 13. Serial Port Mode 2 S3-24 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 IC80C51/31 INTERNAL BUS TB8 TIMER 1 OVERFLOW WRITE TO SBUF 2 SMOD =0 S D Q CL SMOD =1 SBUF TXD ZERO DETECTOR SHIFT DATA TX CONTROL SEND TX CLOCK TI START 16 SERIAL PORT INTERRUPT 16 SAMPLE START LOAD SBUF SHIFT 1FFH RI RX CLOCK 1-TO-0 TRANSITION DETECTOR RX CONTROL BIT DETECTOR INPUT SHIFT REG. (9 BITS) RXD LOAD SBUF SHIFT SBUF READ SBUF IC80C51/31 INTERNAL BUS TX CLOCK WRITE TO SBUF SEND S1P1 DATA TRANSMIT SHIFT START BIT TXD D0 D1 D2 D3 D4 D5 D6 D7 TB8 STOP BIT D3 D4 D5 D6 D7 TI STOP BIT GEN RX CLOCK RXD RECEIVE 16 RESET START BIT D0 D1 D2 RB8 STOP BIT BIT DETECTOR SAMPLE TIMES SHIFT RI Figure 14. Serial Port Mode 3 Integrated Circuit Solution Inc. MC001-0B 25 IC80C51 IC80C31 INTERRUPT SYSTEM The IC80C51/31 provides six interrupt sources: two external interrupts, two timer interrupts, and a serial port interrupt. These are shown in Figure 15. 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. 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, 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 onchip hardware) controls the request flag. 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). 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. POLLING HARDWARE TCON.1 INT0 IE.0 IE.7 HIGH PRIORITY INTERRUPT REQUEST IP.0 EXTERNAL INT RQST 0 IE0 EX0 PX0 TCON.5 IE.1 IP.1 TF0 ET0 PT0 TCON.3 IE.2 IP.2 IE1 EX1 PX1 TCON.7 IE.3 IP.3 TF1 ET1 PT1 SCON.0 INTERNAL RI SERIAL SCON.1 PORT TI IE.4 IP.4 TIMER/COUNTER 0 INT1 SOURCE I.D. VECTOR EXTERNAL INT RQST 1 TIMER/COUNTER 1 ES EA LOW PRIORITY INTERRUPT REQUEST PS SOURCE I.D. VECTOR Figure 15. Interrupt System S3-26 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 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 low-priority interrupt can be interrupted by a high-priority interrupt but not by another low-priority interrupt. A high-priority interrupt can not be interrupted by any other interrupt source. LCALL to the appropriate service routine, provided this hardware generated LCALL is not blocked by any of the following conditions: 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: 3. The instruction in progress is RETI or any write to the IE or IP registers. Source IE0 TF0 IE1 TF1 R1 + T1 1. 2. 3. 4. 5. 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. 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. Priority Within Level (Highest) 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 16. (Lowest) Note that the "priority within level" structure is only used to resolve simultaneous requests of the same priority level. How Interrupts Are Handled Note that if an interrupt of higher priority level goes active prior to S5P2 of the machine cycle labeled C3 in Figure 16, 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. 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 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 S5P2 C1 S6 E INTERRUPT GOES ACTIVE INTERRUPT LATCHED C2 INTERRUPTS ARE POLLED C3 C4 LONG CALL TO INTERRUPT VECTOR ADDRESS C5 INTERRUPT ROUTINE Figure 16. Interrupt Response Timing Diagram Integrated Circuit Solution Inc. MC001-0B 27 IC80C51 IC80C31 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 transitionactivated. 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 shown in the following table. Interrupt Source INT0 Interrupt Request Bits IE0 Timer 0 INT1 TF0 IE1 Timer 1 Serial Port Timer 2 System Reset TF1 RI, TI TF2, EXF2 RST Cleared by Hardware No (level) Yes (trans.) Yes No (level) Yes (trans.) Yes No No Vector Address 0003H 000BH 0013H 001BH 0023H 002BH 0000H 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. Interrupt External 0 External 1 Timer 1 Timer 0 Serial Port Serial Port S3-28 Flag IE0 IE1 TF1 TF0 TI RI SFR Register and Bit Position TCON.1 TCON.3 TCON.7 TCON.5 SCON.1 SCON.0 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. 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. Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 Response Time Single-Step Operation 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 IC80C51/31 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 re-entered 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, INT0) to be level-activated. The service routine for the interrupt will terminate with the following code: 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. 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). JNB P3.2,$ ;Wait Here Till INT0 Goes High 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 INT0 is pulsed (from low-tohigh-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. Thus, in a single-interrupt system, the response time is always more than three cycles and less than nine cycles. Integrated Circuit Solution Inc. MC001-0B 29 IC80C51 IC80C31 OTHER INFORMATION Table 9. Reset Values of the SFR's SFR Name PC ACC Reset The reset input is the RST pin, which is the input to a Schmitt Trigger. Reset Value 0000H 00H B PSW SP DPTR P0-P3 IP IE TMOD TCON TH0 TL0 TH1 TL1 SCON SBUF PCON A reset is accomplished by holding the RST pin high for at least two machine cycles (24 oscillator periods), while the oscillator is running. The CPU responds by generating an internal reset, with the timing shown in Figure 17. 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 9 lists the SFRs and their reset values. Then internal RAM is not affected by reset. On power-up the RAM content is indeterminate. 00H 00H 07H 0000H FFH XX000000B 0X000000B 00H 00H 00H 00H 00H 00H 00H Indeterminate 0XXX0000B 12 OSC. PERIODS S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 RST INTERNAL RESET SIGNAL SAMPLE RST SAMPLE RST ALE PSEN P0 INST ADDR INST 11 OSC. PERIODS ADDR INST ADDR INST ADDR INST ADDR 19 OSC. PERIODS Figure 17. Reset Timing S3-30 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 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 and the oscillator start-up time does not exceed 10 msec. For the IC80C51/31, the external resistor can be removed because the RST pin has an internal pulldown. The capicator value can then be reduced to 1µF (see Figure 18). 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. 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. Vcc 1.0 F + Vcc IC80C51/31 RST GND Figure 18. Power-On Reset Circuit 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. Integrated Circuit Solution Inc. MC001-0B 31 IC80C51 IC80C31 Power-Saving Modes of Operation The IC80C51/31 has two power-reducing modes. Idle and Power-down. The input through which backup power is supplied during these operations is Vcc. Figure 19 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. XTAL 1 XTAL 2 OSC INTERRUPT, SERIAL PORT, TIMER BLOCKS CLOCK GEN CPU PD IDL 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. Figure 19. 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 PSEN 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. 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 17, 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. S3-32 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 Table 10. Status of the External Pins During Idle and Power-down Modes. Mode Memory ALE PSEN 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 IC80C51/31 is a single stage inverter, intended for use as a crystal-controlled, positive reactance oscillator. 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 20). Examples of how to drive the clock with external oscillator are shown in Figure 21. The crystal specifications and capacitance values (C1 and C2 in Figure 20) are not critical. 20 pF to 30 pF can be used in these positions at a 12 MHz to 24 MHz frequency with good quality crystals. (For ranges greater than 24 MHz refer to Figure 21.) 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. C2 XTAL2 C1 XTAL1 GND Figure 20. Oscillator Connections Integrated Circuit Solution Inc. MC001-0B NC EXTERNAL OSCILLATOR SIGNAL XTAL2 XTAL1 GND Figure 21. External Clock Drive Configuration 33 IC80C51 IC80C31 XTAL2 XTAL1 R C2 C1 Figure 22. Oscillator Connections for High Speed (> 24 MHz) Note: When the frequency is higher than 24 MHz, please refer to Table 11 for recommended values of C1, C2, and R. Table 11. Recommended Value for C1, C2, R C1 C2 R S3-34 Frequency Range 3.5 MHz - 24 MHz 24 MHz - 40 MHz 20 pF-30 pF 3 pF-10 pF 20 pF-30 pF 3 pF-10 pF Not Apply 6.2K-10K Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 ROM Verification The address of the program menory location to be read is applied to Port 1 and pins P2.3-P2.0. The other pins should be held at the “Verify” level . The contents of the addressed locations will be emitted on Port 0. External pullups are required on Rort 0 for this operation. Figure 23 shows the setup to verify the program memory. + 5V A7-A0 P1 A11-A8 P2.3-P2.0 1 RST 1 EA 1 ALE 0 PSEN 0 P2.7 0 P2.6 Vcc 10K x 8 P0 PGM DATA XTAL1 4-6 MHz XTAL2 GND Figure 23. ROM Verification Integrated Circuit Solution Inc. MC001-0B 35 IC80C51 IC80C31 ABSOLUTE MAXIMUM RATINGS(1) Symbol VTERM TBIAS TSTG PT Parameter Terminal Voltage with Respect to GND(2) Temperature Under Bias(3) Storage Temperature Power Dissipation Value –2.0 to +7.0 0 to +70 –65 to +125 1.5 Unit V °C °C 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 Commercial Ambient Temperature 0°C to +70°C VCC 5V ± 10% Oscillator Frequency 3.5 to 40 MHz Note: 1. Operating ranges define those limits between which the functionality of the device is guaranteed. S3-36 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 DC CHARACTERISTICS (Ta=0°C to 70 °C; VCC=5V+10%; VSS=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 (All except XTAL 1, RST) 0.2Vcc + 0.9 Vcc + 0.5 V VIH1 Input high voltage (XTAL 1) 0.7Vcc Vcc + 0.5 V VSCH+ RST positive schmitt-trigger threshold voltage 0.7Vcc Vcc + 0.5 V VSCH– RST negative schmitt-trigger threshold voltage 0 0.2Vcc V VOL(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 IOL = 7.0 mA — 1.0 V IOH = –10 µA Vcc = 4.5V-5.5V 0.9Vcc — V IOL = –25 µA 0.75Vcc — V IOL = –60 µA 2.4 — V IOH = –80 µA Vcc = 4.5V-5.5V 0.9Vcc — V IOH = –300 µA 0.75Vcc — V IOH = –800 µA 2.4 — V — –110 µA –10 +10 µA — –650 µA 50 300 KΩ (1) VOL1 VOH VOH1 Output high voltage (Ports 1, 2, 3, ALE, PSEN) Output high voltage (Port 0, ALE, PSEN) IIL Logical 0 input current (Ports 1, 2, 3) VIN = 0.45V ILI Input leakage current (Port 0) 0.45V < VIN < Vcc ITL Logical 1-to-0 transition current (Ports 1, 2, 3) VIN = 2.0V RRST RST pulldown resister Note: 1. Under steady state (non-transient) conditions, IOL must be externally limited as follows: Maximum IOL per port pin: 10 mA Maximum IOL per 8-bit port Port 0: 26 mA Ports 1, 2, 3: 15 mA Maximum total IOL for all output pins: 71 mA If IOL exceeds the test condition, VOL may exceed the related specification. Integrated Circuit Solution Inc. MC001-0B 37 IC80C51 IC80C31 POWER SUPPLY CHARACTERISTICS Symbol Parameter Test conditions (1) Icc Min Max Unit Power supply current Vcc = 5.0V Active mode 12 MHz — 20 mA 16 MHz — 26 mA 20 MHz — 32 mA 24 MHz — 38 mA 32 MHz — 50 mA 40 MHz — 62 mA 12 MHz — 5 mA 16 MHz — 6 mA 20 MHz — 7.6 mA 24 MHz — 9 mA 32 MHz — 12 mA 40 MHz — 15 mA VCC = 5V — 100 µA Idle mode Power-down mode Note: 1. See Figures 24,25,26, and 27 for Icc test conditiions. Vcc Vcc Vcc Icc Icc RST RST Vcc Vcc Vcc Vcc NC XTAL2 CLOCK SIGNAL XTAL1 GND P0 EA NC XTAL2 CLOCK SIGNAL XTAL1 GND P0 EA Figure 25. Idle Mode Figure 24. Active Mode Vcc Icc RST Vcc Vcc NC XTAL2 P0 XTAL1 GND EA Figure 26. Power-down Mode S3-38 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 tCLCX Vcc — 0.5V 0.45V tCHCX 0.7Vcc 0.2Vcc — 0.1 tCHCL tCLCH tCLCL Figure 27. Clock Signal Waveform for I CC Tests in Active and Idle Mode (tCLCH=t CHCL=5 ns) AC CHARACTERISTICS (Ta=0°C to 70 °C; VCC=5V+10%; GND=0V; C1 for Port 0, ALE and PSEN Outputs=100pF; C1 for other outputs=80pF) EXTERNAL MEMORY CHARACTERISTICS Symbol 1/tCLCL tLHLL tAVLL tLLAX tLLIV tLLPL tPLPH tPLIV tPXIX tPXIZ tAVIV tPLAZ tRLRH tWLWH tRLDV tRHDX tRHDZ tLLDV tAVDV tLLWL tAVWL tQVWX tWHQX tRLAZ tWHLH Parameter Oscillator frequency ALE pulse width Address valid to ALE low Address hold after ALE low ALE low to valid instr in ALE low to PSEN low PSEN pulse width PSEN low to valid instr in Input instr hold after PSEN Input instr float after PSEN Address to valid instr in PSEN low to address float RD pulse width WR pulse width RD low to valid data in Data hold after RD Data float after RD ALE low to valid data in Address to valid data in ALE low to RD or WR low Address to RD or WR low Data valid to WR transition Data hold after WR RD low to address float RD or WR high to ALE high Integrated Circuit Solution Inc. MC001-0B 24 MHz Clock Min Max — — 68 — 26 — 31 — — 147 31 — 110 — — 105 0 — — 37 — 188 — 10 230 — 230 — — 157 0 — — 78 — 282 — 323 105 145 146 — 26 — 31 — — 0 26 57 40 MHz Clock Min Max — — 35 — 10 — 15 — — 80 15 — 60 — — 55 0 — — 20 — 105 — 10 130 — 130 — — 90 0 — — 45 — 165 — 190 55 95 80 — 10 — 15 — — 0 10 40 Variable Oscillator (3.5 - 40 MHz) Min Max 3.5 40 2tCLCL–15 — tCLCL–15 — tCLCL–10 — — 4tCLCL–20 tCLCL–10 — 3tCLCL–15 — — 3tCLCL–20 0 — — tCLCL–5 — 5tCLCL–20 — 10 6tCLCL–20 — 6tCLCL–20 — — 4tCLCL–10 0 — — 2tCLCL–5 — 7tCLCL–10 — 8tCLCL–10 3tCLCL–20 3tCLCL+20 4tCLCL–20 — tCLCL–15 — tCLCL–10 — — 0 tCLCL–15 tCLCL+15 Unit MHz ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns 39 IC80C51 IC80C31 EXTERNAL MEMORY CHARACTERISTICS Symbol tXLXL tQVXH tXHQX tXHDX tXHDV Parameter Serial port clock cycle time Output data setup to clock rising edge Output data hold after clock rising edge Input data hold after clock rising edge Clock rising edge to input data valid 24 MHz Clock Min Max 490 510 406 — 40 MHz Clock Min Max 290 310 240 — Variable Oscillator (3.5-40 MHz) Min Max 12tCLCL–10 12tCLCL+10 10tCLCL–10 — 73 — 40 — 2tCLCL–10 — ns 0 — 0 — 0 — ns — 417 — 250 — 10tCLCL ns Min 3.5 10 10 — — Max 40 — — 10 10 Unit MHz ns ns ns ns Min 4 — — 0 Max 6 40tCLCL 48tCLCL 48tCLCL Unit MHz Unit ns ns EXTERNAL CLOCK DRIVE Symbol 1/tCLCL tCHCX tCLCX tCLCH tCHCL Parameter Oscillator Frequency High time Low time Rise time Fall time ROM VERIFICATION CHARACTERISTICS Symbol 1/tCLCL tAVQV tELQV tEHQZ S3-40 Parameter Oscillator Frequency Address to data valid ENABLE low to data valid Data float after ENABLE Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 TIMING WAVEFORMS tLHLL ALE tLLPL tPLPH tPLIV tAVLL PSEN tPLAZ tLLAX PORT 0 A7-A0 tPXIX tPXIZ INSTR IN A7-A0 tLLIV tAVIV PORT 2 A15-A8 A15-A8 Figure 28. External Program Memory Read Cycle ALE tWHLH PSEN tLLDV tLLWL RD PORT 0 tAVLL tRLAZ tLLAX tRLRH tRLDV A7-A0 FROM RI OR DPL tRHDZ tRHDX DATA IN A7-A0 FROM PCL INSTR IN tAVWL tAVDV PORT 2 A15-A8 FROM DPH A15-A8 FROM PCH Figure 29. External Data Memory Read Cycle Integrated Circuit Solution Inc. MC001-0B 41 IC80C51 IC80C31 ALE tWHLH PSEN tLLWL WR tWLWH tAVLL PORT 0 tWHQX tQVWX tLLAX A7-A0 FROM RI OR DPL DATA OUT A7-A0 FROM PCL INSTR IN tAVWL PORT 2 A15-A8 FROM DPH A15-A8 FROM PCH Figure 30. External Data Memory Write Cycle INSTRUCTION 0 1 2 3 4 5 6 7 8 ALE tXLXL CLOCK tXHQX tQVXH 0 DATAOUT 1 tXHDV DATAIN VALID VALID 2 tXHDX VALID 3 4 5 6 7 SET TI VALID VALID VALID VALID VALID SET RI Figure 31. Shift Register Mode Timing Waveform tCLCX Vcc — 0.5V 0.45V tCHCX 0.7Vcc 0.2Vcc — 0.1 tCHCL tCLCH tCLCL Figure 32. External Clock Drive Waveform S3-42 Integrated Circuit Solution Inc. MC001-0B IC80C51 IC80C31 P1.0-P1.7 P2.0-P2.3 ADDRESS PORT 0 DATA OUT tAVQV tELQV tEHQZ P2.7 Figure 33. ROM Verification Waveforms Vcc - 0.5V 0.45V 0.2Vcc + 0.9V 0.2Vcc - 0.1V Figure 34. 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 VIH min for logic “1” and max for logic “0”. Integrated Circuit Solution Inc. MC001-0B 43 IC80C51 IC80C31 ORDERING INFORMATION Commercial Temperature: 0°C to +70°C Speed 12 MHz 24 MHz 40 MHz 12MHz 24MHz 40MHz Order Part Number IC80C51-12PL IC80C51-12PQ IC80C51-12W IC80C51-24PL IC80C51-24PQ IC80C51-24W IC80C51-40PL IC80C51-40PQ IC80C51-40W IC80C31-12PL IC80C31-12PQ IC80C31-12W IC80C31-24PL IC80C31-24PQ IC80C31-24W IC80C31-40PL IC80C31-40PQ IC80C31-40W Package PLCC PQFP 600mil DIP PLCC PQFP 600mil DIP PLCC PQFP 600mil DIP PLCC PQFP 600mil DIP PLCC PQFP 600mil DIP PLCC PQFP 600mil DIP Integrated Circuit Solution Inc. HEADQUARTER: NO.2, TECHNOLOGY RD. V, SCIENCE-BASED INDUSTRIAL PARK, HSIN-CHU, TAIWAN, R.O.C. TEL: 886-3-5780333 Fax: 886-3-5783000 BRANCH OFFICE: 7F, NO. 106, SEC. 1, HSIN-TAI 5TH ROAD, HSICHIH TAIPEI COUNTY, TAIWAN, R.O.C. TEL: 886-2-26962140 FAX: 886-2-26962252 http://www.icsi.com.tw S3-44 Integrated Circuit Solution Inc. MC001-0B