问答题
下面是一个系统对2片8259A作初始化的程序段,主片地址为50H和52H,从片地址为60H和62H。请加注释。 KKK:CLI MOV AL,1DH OUT 40H,AL MOV AL,80H OUT 52H,AL MOV AL,08H OUT 52H,AL MOV AL,1FH OUT 52H,AL CLI MOV AL,19H OUT 60H,AL MOV AL,90H OUT 62H,AL MOV AL,03H OUT 62H. AL MOV AL,0BH OUT 62H,AL
【正确答案】注释程序段如下: KKK:CLI ;对主片初始化 MOV AL,1DH ;主片ICW1,级联,电平触发 OUT 40H,AL MOV AL,80H ;主片ICW2,中断类型号为50H~57H OUT 52H,AL MOV AL,08H ;主片ICW3,有从片,主片IR3接从片 OUT 52H,AL MOV AL,1FH ;主片ICW4,特殊全嵌套,缓冲方式,中断自动结束方式 OUT 52H,AL CLI ;从片初始化 MOV AL,19H OUT 60H,AL ;从片ICW1,级联,边沿触发 MOV AL,90H OUT 62H,AL ;从片ICW2,中断类型号为90H~97H MOV AL,03H OUT 62H,AL ;从片ICW3,从片在主片的IR3 MOV AL,0BH OUT 62H,AL ;全嵌套,缓冲方式,自动结束