1. I/O Interfacing
CSE 2312
Maher Al-Khaiyat

2. I/O Instructions I/O address space I/O ports for data transfer
IN and OUT instructions
8-bit and 16-bit data ports
Control signals: IOR and IOW
Communication called peripheral I/O

3. 8-bit Ports IN OUT IN dest, source IN AL, port# MOV DX, port# IN AL,DX
OUT dest, source
OUT port#, AL
MOV DX, port#
OUT DX,AL
Port address 00h-FFh
Address bus A0-A7
No segment register involved
Port address 0000h-FFFFh
Address bus A0-A15
No segment register involved

4. I/O 8255 Chip Programmable Peripheral Interface (PPI)
3 ports for input or output
4 addressable locations (3 ports plus control register)

5. I/O Address Map HEX Range Description 0000 001F
DMA controller 1, 8237A-5
0020
003F
Interrupt controller 1, 8259A, Master
0040
005F
Timer, …
0378
037F
Parallel printer port 1
03F8
03FF
Serial port 1

6. C/C++ I/O Programming IN OUT IN OUT IN AL, port# IN AL,DX
Assembly
C/C++ IN
IN AL, port#
IN AL,DX
OUT
OUT port#, AL
OUT DX,AL IN
_inp(port#)
OUT
_outp(port#,byte)