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