8086/8088 Hardware System

Typical Microprocessor Memory System CPU Memory Control Address Data

8086/8088 Memory Interface Address Bus –20 address lines so a 2 20 byte address space –Pins A0-A19 provide the address –For 8086, A0-A15 appear multiplexed with D0-D15 to form AD0-AD15 –For 8088, A0-A7 appear multiplexed with D0-D7 to form AD0-AD7 Data Bus –For 8086, 16 bit data bus D0-D15 (multiplexed as AD0-AD15) –For 8088, 8 bit data bus D0-D7 (multiplexed as AD0-AD7) –8086 may use only D0-D7 or D8-D15 if appropriate Control Bus –For memory access, the following pins are used: –RD’, WR’, M/IO’, DT/R’, DEN’, ALE, BHE’

8086/8088 Pin Configuration

8086/8088 Pin Configuration Differences

Clock Generator

8284A

8086/8088 Detailed Memory Interface 8086/8 Control Multiplexed Addr/Data Latches Buffers Demultiplexing Control Address Data Address Decoding Unique per device MEMORYMEMORY Partial Address CS’,WE’,OE’

8088 Bus Structure

‘244

‘245

‘373

Address Decoding Example 1

2716

4016

Address Decoding Example 2

‘138

Input via Switches

Output via LEDs

7 Segment LED Driver

7 segment display a b c g d e f Digit-abcdefg-hex E D B F F B A B F C ED D E FF

8255 Programmable Peripheral Interface

8255 Control Byte

8255 Clock Example PA7-PA D0-D7 A0-A1 RD’ WR’ CS’ Assume CS selects for 0F00H-0F03H HourMinuteSecond PC3-PC0 PB7-PB4 PA3-PA0 PB3-PB0 PC7-PC4 7447

8255 Clock Example Code MOV DX,0F03H;8255 control register MOV AL,80H;select all ports to mode 0 output OUT DX,AL;set 8255 control MOV AH,2;read real time clock INT 1AH;CH=hour(BCD),CL=minute,DH=seconds MOV AL,CH MOV DX,0F00H OUT DX,AL MOV AL,CL MOV DX,0F01H OUT DX,AL MOV AL,DH MOV DX,0F02H OUT DX,AL

8255 Clock Example 2 PA D0-D7 A0-A1 RD’ WR’ CS’ Assume CS selects for 0F00H-0F03H HourMinute PB6-PB0 PA6-PA0 PC6-PC0

8255 Clock Example 2 Code.DATA SEG7 DB 7EH,30H,6DH,79H,33H,5BH,5FH,70H,7FH,7BH DB 0,0,0,0,0,0,0FEH,0B0H,0EDH.CODE MOV AH,2 INT 1AH LEA BX,SEG7 MOV AL,CH XLAT MOV DX,0F00H OUT DX,AL

8255 Clock Example 2 Code cont. MOV AL,CH SHR AL,4 XLAT MOV DX,0F01H OUT DX,AL MOV AL,CH AND AL,0FH XLAT MOV DX,0F02H OUT DX,AL

16550 Serial Communications Interface

16550

Digital to Analog Conversion

DAC0830

Analog to Digital Conversion

ADC0804