8255A编程（高分急）

1、片选端口地址；A端口地址为218h,B端口地址为219h,C端口地址为21Ah,执行端口地址为21Bh
2、A端口输入方式0，B端口输出方式0
3、START: MOV DX,21BH
MOV AL,99H
MOV DX,AL

4、CODE SEGMENT
ASSUME CS:CODE
START: MOV DX,21BH
MOV AL,99H
MOV DX,AL

AGAIN: MOV DX,18H
IN AL,DX
CMP AL,OH
JZ LOOO
CMP AL,O1H
JZ LOO1
CMP AL,O2H
JZ LOO2
CMP AL,O3H
JZ LOO3
CMP AL,O4H
JZ LOO4
CMP AL,O5H
JZ LOO5
CMP AL,O6H
JZ LOO6
CMP AL,O7H
JZ LOO7
JMP AGAIN
LOOO: MOV AL,00H
MOV DX,219H
OUT DX,AL
JMP AGAIN
LOO1: MOV AL,01H
MOV DX,219H
OUT DX,AL
JMP AGAIN
LOO2: MOV AL,02H
MOV DX,219H
OUT DX,AL
JMP AGAIN
LOO3: MOV AL,03H
MOV DX,219H