8086/8088 hardware system. typical microprocessor memory system cpu memory control address data

8086/8088 Hardware System

Typical Microprocessor Memory System

CPU Memory

Control

Address

Data

8086/8088 Memory Interface• Address Bus

– 20 address lines so a 220 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

MEMORY

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 displaya

b

c

g

d

e

f Digit-abcdefg-hex

0-1111110-7E 1-0110000-30

2-1101101-6D 3-1111001-79

4-0110011-33 5-1011011-5B

6-1011111-5F 7-1110000-70

8-1111111-7F 9-1111011-7B

A-1110111-77 B-0011111-1F

C-1001110-4E D-0111101-3D

E-1001111-4F F-1000111-47

8255 Programmable Peripheral Interface

8255 Control Byte

8255 Clock Example

PA7-PA4

8255

D0-D7

A0-A1

RD’

WR’

CS’

Assume CS selects for 0F00H-0F03H

Hour Minute Second

PC3-PC0

PB7-PB4PA3-PA0

PB3-PB0PC7-PC4

7447 7447 7447 7447 7447 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

PA7

8255

D0-D7

A0-A1

RD’

WR’

CS’

Assume CS selects for 0F00H-0F03H

Hour Minute

PB6-PB0PA6-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