1. 8253/54实时时钟控制器
Counter 0 Address 304H
Counter 1 Address 305H
Counter 2 Address 306H
Counter Control register Address 307H
2. 8259A可编程中断控制器
ICW1 port 26h
ICW2,ICW3,ICW4 port 27h
3. 8255A可编程外围接口
port A Address 60h
port B Address 61h
port C Address 62h
port Control register Address 63h