端口地址
在微机系统中，每个端口 分配有唯一的地址码，称之为端口地址。
I/O端口地址表
Port addresses are not always constant across PC, AT and PS2
Unless marked, port addresses are relative to PC and XT only
000-00F 8237 DMA controller:
000 Channel 0 address register
001 Channel 0 word count
002 Channel 1 address register
003 Channel 1 word count
004 Channel 2 address register
005 Channel 2 word count
006 Channel 3 address register
007 Channel 3 word count
008 Status/command register
009 Request register
00A Mask register
00B Mode register
00C Clear MSB/LSB flip flop
00D Master clear temp register
00E Clear mask register
00F Multiple mask register
010-01F 8237 DMA Controller (PS2 model 60 & 80), reserved (AT)
020-02F 8259A Master Programmable Interrupt Controller:
020 8259 Command port (see 8259)
021 8259 Interrupt mask register (see 8259)
030-03F 8259A Slave Programmable Interrupt Controller (AT,PS2)
040-05F 8253 or 8254 Programmable Interval Timer:
040 8253 channel 0, counter divisor
041 8253 channel 1, RAM refresh counter
042 8253 channel 2, Cassette and speaker functions
043 8253 mode control (see 8253)
044 8254 PS/2 extended timer
047 8254 Channel 3 control byte
060-067 8255 Programmalbe Peripheral Interface (PC,XT,PCjr):
060 8255 Port A keyboard input/output buffer (output PCjr)
061 8255 Port B output
062 8255 Port C input
063 8255 Command/Mode control register
060-06f 8042 Keyboard Controller (AT,PS2):
060 8042 Keyboard input/output buffer register
061 8042 system control port (for compatability with 8255)
064 8042 Keyboard command/status register
070 CMOS RAM/RTC, also NMI enable/disable (AT,PS2, see RTC)
071 CMOS RAM data (AT,PS2)
080 Manufacturer checkpoint port
080-090 DMA Page Registers:
081 High order 4 bits of DMA channel 2 address
082 High order 4 bits of DMA channel 3 address
083 High order 4 bits of DMA channel 1 address
090-097 POS/Programmable Option Select (PS2):
090 Central arbitration control Port
091 Card selection feedback
092 System control and status register
094 System board enable/setup register
095 Reserved
096 Adapter enable/setup register
097 Reserved
0A0 NMI Mask Register (PC,XT) (write 80h to enable NMI, 00h disable)
0A0-0BF Second 8259 Programmalbe Interrupt Controller (AT,PS2):
0A0 Second 8259 Command port (see 8259)
0A1 Second 8259 Interrupt mask register (see 8259)
0C0 TI SN76496 Programmable Tone/Noise Generator (PCjr)
0C0-0DF 8237 DMA Controller 2 (AT):
0C2 DMA channel 3 selector (see ports 6 & 82)
0E0-0EF Reserved
0F0-0FF Math Coprocessor (AT,PS2)
0F0-0F5 PCjr Disk Controller:
0F0 Disk Controller
0F2 Disk Controller control port
0F4 Disk Controller status register
0F5 Disk Controller data port
0F8-0FF Reserved for future microprocessor extensions
100-10F POS Programmable Option Select (PS2):
100 POS Register 0, Adapter ID byte (LSB)
101 POS Register 1, Adapter ID byte (MSB)
102 POS Register 2, Option select data byte 1
Bit 0 is card enable (CDEN)
103 POS Register 3, Option select data byte 2
104 POS Register 4, Option select data byte 3
105 POS Register 5, Option select data byte 4
Bit 7 is (-CHCK)
Bit 6 is reserved
106 POS Register 6, subaddress extension (LSB)
107 POS Register 7, subaddress extension (MSB)
110-1EF System I/O channel
170-17F Fixed disk 1 (AT):
170 disk 1 data
171 disk 1 error
172 disk 1 sector count
173 disk 1 sector number
174 disk 1 cylinder low
175 disk 1 cylinder high
176 disk 1 drive/head
177 disk 1 status
1F0-1FF Fixed disk 0 (AT):
1F0 disk 0 data
1F1 disk 0 error
1F2 disk 0 sector count
1F3 disk 0 sector number
1F4 disk 0 cylinder low
1F5 disk 0 cylinder high
1F6 disk 0 drive/head
1F7 disk 0 status
200-20F Game Adapter
210-217 Expansion Card Ports (XT):
210 Write: latch expansion bus data
read: verify expansion bus data
211 Write: clear wait,test latch
Read: MSB of data address
212 Read: LSB of data address
213 Write: 0=enable, 1=/disable expansion unit
214-215 Receiver Card Ports
214 write: latch data, read: data
215 read: MSB of address, next read: LSB of address
21F Reserved
220-26F Reserved for I/O channel
270-27F Third parallel port (see PARALLEL PORT):
278 data port
279 status port
27A control port
280-2AF Reserved for I/O channel
2A2-2A3 MSM58321RS clock