Suranaree University Of Technology มทส 2002 Anant Oonsivilai 2002/2/25 Microcomputers and Microprocessors 1 Chapter 4 I/O Port Programming

2002/2/252002/2/25 Microcomputers and MicroprocessorsMicrocomputers and Microprocessors 11

Suranaree UniversitySuranaree University

Of TechnologyOf Technologyมทสมทส

2002 Anant Oonsivilai2002 Anant Oonsivilai

Chapter 4Chapter 4I/O Port ProgrammingI/O Port Programming

222002/2/252002/2/25 Microcomputers and MicroprocessorsMicrocomputers and Microprocessors2002 Anant Oonsivilai2002 Anant Oonsivilai

OutlinesOutlines

8051 pin functions8051 pin functions

4 ports of 80514 ports of 8051

Dual role of port 0 for data & addressDual role of port 0 for data & address

Code assembly language to use portsCode assembly language to use ports

Use of port 3 for interrupt signalsUse of port 3 for interrupt signals

Code 8051 instructions for I/O handlingCode 8051 instructions for I/O handling

Code bit-manipulation instructionsCode bit-manipulation instructions


8051 Pin Diagram8051 Pin Diagram


Clock GenerationClock Generation


Clock GenerationClock Generation


Machine & Clock CyclesMachine & Clock Cycles


RESET Value of RegistersRESET Value of Registers


RESET CircuitsRESET Circuits


RESET CircuitsRESET Circuits


Pins for External ROM/RAMPins for External ROM/RAM

EA (external access)EA (external access) VVCCCC: on-chip ROM: on-chip ROM GND: external ROMGND: external ROM

PSEN (program store enable)PSEN (program store enable) to OE (output enable) pin of ROMto OE (output enable) pin of ROM

ALE (address latch enable)ALE (address latch enable) to G (enable) pin of 74LS373to G (enable) pin of 74LS373

See See Chapter 14Chapter 14


Port 0: I/O, Open DrainPort 0: I/O, Open Drain

Initially configured as outputInitially configured as output

MOVMOV A,#55H A,#55H

BACK:BACK: MOV MOV P0,A P0,A

ACALL DELAYACALL DELAY

CPLCPL A A

SJMPSJMP BACK BACK


Port 0: I/O, Open DrainPort 0: I/O, Open Drain


Port 0 as Input: Write all 1sPort 0 as Input: Write all 1s

Dual role of port 0Dual role of port 0 Can be configured as AD0 – AD7Can be configured as AD0 – AD7

MOV A,#0FFH ;A = FF hex

MOV P0,A ;make P0 an input port

;by writing all 1s to it

BACK: MOV A,P0 ;get data from P0

MOV P1,A ;send it to port 1

SJMP BACK ;keep doing it


Port 1: I/O, No Pull-up ResistorsPort 1: I/O, No Pull-up Resistors

Initially configured as outputInitially configured as output

MOV A,#55H

BACK: MOV P1,A

ACALL DELAY

CPL A

SJMP BACK

MOV A,#0FFH ;A=FF hex

MOV P1,A ;make P1 an input port

;by writing all 1s to it

MOV A,P1 ;get data from P1

MOV R7,A ;save it in reg R7

ACALL DELAY ;wait

MOV A,P1 ;get another data from P1


ACALL DELAY ;wait

MOV A,P1 ;get another data from P1




Initially configured as outputInitially configured as outputMOV A,#55H

BACK: MOV P2,AACALL DELAYCPL ASJMP BACK

MOV A,#0FFH ;A=FF hexMOV P2,A ;make P2 an input port by

;writing all 1s to itBACK: MOV A,P2 ;get data from P2

MOV P1,A ;send it to Port 1SJMP BACK ;keep doing that

Dual role of port 2: A8-A15Dual role of port 2: A8-A15




Different Ways of Accessing 8 bitsDifferent Ways of Accessing 8 bits

BACK:BACK: MOVMOV A,#55HA,#55H

MOVMOV P1,AP1,A

ACALLACALL DELAYDELAY

MOVMOV A,#0AAHA,#0AAH

MOVMOV P1,AP1,A


SJMPSJMP BACKBACK

BACK:BACK: MOVMOV P1,#55HP1,#55H


MOVMOV P1,#0AAHP1,#0AAH


SJMPSJMP BACKBACK

MOV P1,#55H ;P1=01010101AGAIN: XLR P1,#0FFH ;EX-OR

;P1 with 1111 1111 ACALL DELAY SJMP AGAIN


Single-bit Addressability of Single-bit Addressability of PortsPorts

BACK:BACK: CPLCPL P1.2P1.2 ;complement P1.2 only;complement P1.2 only


SJMPSJMP BACKBACK

;another variation of the above program follows;another variation of the above program follows

AGAIN:AGAIN: SETBSETB P1.2P1.2 ;change only P1.2=high;change only P1.2=high


CLRCLR P1.2P1.2 ;change only P1.2=low;change only P1.2=low


SJMPSJMP AGAINAGAIN


Single-bit Addressability of Single-bit Addressability of PortsPorts


Example 4-2Example 4-2

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Suranaree University Of Technology มทส 2002 Anant Oonsivilai 2002/2/25 Microcomputers and Microprocessors 1 Chapter 4 I/O Port Programming