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Common I/O Port Addresses
Port addresses are not always constant across PC, AT and PS/2
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 (PS/2), reserved (AT)
020-02F 8259A Programmable Interrupt Controller (all machines)
030-03F 8259A Programmable Interrupt Controller (AT only)
020 8259 Command port (see 8259)
021 8259 Interrupt mask register (see 8259)
040-05F 8253-5 Programmable Interval Timer (PIT, see 8253)
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)
060-06F 8042 Keyboard Controller (AT)
060-067 8255 Programmable Peripheral Interface
060 Port A input (keyboard scan code) (PC1,PC2,XT) (output PCjr)
061 Port B output (PC1,PC2,XT,PCjr)
062 Port C input (PC1,PC2,XT,PCjr)
063 Command/Mode control register
070 Real Time Clock, CMOS config memory & NMI mask (AT,PS2)
080 Manufacturer checkpoint port
080-09F 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
0A0 NMI Mask Register (PC,XT) (write 80h to enable NMI,
00h disable)
0A0-0BF Second 8259 Programmable Interrupt Controller (AT, PS2)
0A0 Second 8259 Command port (see 8259)
0A1 Second 8259 Interrupt mask register (see 8259)
0C0-0DF 8237 DMA controller 2 (AT)
0C0 TI SN76496 Programmable Tone/Noise Generator (PCjr)
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
100-10F Programmable Option Select (PS2)
110-1EF System I/O channel
1F0-1FF Fixed disk (AT)
200-20F Game Adapter (see GAME PORT or JOYSTICK)
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 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
220-26F Reserved for I/O channel
270-27F Third parallel port (see PARALLEL PORT)
280-2AF Reserved for I/O channel
2B0-2DF Alternate EGA, or 3270 PC video (XT, AT)
2E8-2EF COM4 non PS/2 UART (Reserved by IBM) (see UART)
2F0-2F7 Reserved
2F8-2FF COM2 Second Asynchronous Adapter (see UART)
Primary Asynchronous Adapter for PCjr
300-31F Prototype Experimentation Card (except PCjr)
320-32F Hard Disk Controller (XT)
320 Read from/Write to controller
321 Read: Controller Status, Write: controller reset
322 Write: generate controller select pulse
323 Write: Pattern to DMA and interrupt mask register
(see ports 0F,21,C2)
330-33F Reserved for XT/370
340-35F Reserved for I/O channel
360-36F PC Network
378-37F Second Parallel Printer (see PARALLEL PORT)
First Parallel Printer (see PARALLEL PORT)
380-38F Synchronous Data Link Control (SDLC) Adapter
380-389 Second Binary Synchronous Adapter (if first is
already installed) (see ports 3A0-3A9 for mapping)
380 On board 8255 port A, internal/external sense
381 On board 8255 port B, external modem interface
382 On board 8255 port C, internal control and gating
383 On board 8255 mode register
384 On board 8253 channel square wave generator
385 On board 8253 channel 1 inactivity time-out
386 On board 8253 channel 2 inactivity time-out
387 On board 8253 mode register
388 On board 8273 read: status; Write: Command
389 On board 8273 write: parameter; read: response
38A On board 8273 transmit interrupt status
38B On board 8273 receiver interrupt status
38C On board 8273 data
390-39F Cluster Adapter
3A0-3AF Primary Bisynchronous Adapter
3A0 On board 8255 port A, internal/external sense
3A1 On board 8255 port B, external modem interface
3A2 On board 8255 port C, internal control and gating
3A3 On board 8255 mode register
3A4 On board 8253 counter 0 not used
3A5 On board 8253 counter 1 inactivity time-outs
3A6 On board 8253 counter 2 inactivity time-outs
3A7 On board 8253 mode register
3A8 On board 8251 data
3A9 On board 8251 command/mode/status register
3B0-3BF Monochrome Display Adapter (write only, see 6845)
3B0 port address decodes to 3B4
3B1 port address decodes to 3B5
3B2 port address decodes to 3B4
3B3 port address decodes to 3B5
3B4 6845 index register, selects which register [0-11h]
is to be accessed through port 3B5
3B5 6845 data register [0-11h] selected by port 3B4,
registers 0C-0F may be read. If a read occurs without
the adapter installed, FFh is returned. (see 6845)
3B6 port address decodes to 3B4
3B7 port address decodes to 3B5
3B8 6845 Mode control register
3B9 reserved for color select register on color adapter
3BA status register (read only)
3BB reserved for light pen strobe reset
3BC-3BF Primary Parallel Printer Adapter (see PARALLEL PORT)
3C0-3CF Enhanced Graphics Adapter
3D0-3DF Color Graphics Monitor Adapter (ports 3D0-3DB are
write only, see 6845)
3D0 port address decodes to 3D4
3D1 port address decodes to 3D5
3D2 port address decodes to 3D4
3D3 port address decodes to 3D5
3D4 6845 index register, selects which register [0-11h]
is to be accessed through port 3D5
3D5 6845 data register [0-11h] selected by port 3D4,
registers 0C-0F may be read. If a read occurs without
the adapter installed, FFh is returned. (see 6845)
3D6 port address decodes to 3D4
3D7 port address decodes to 3D5
3D8 6845 Mode control register (except PCjr)
3D9 color select register (see 6845)
3DA status register (read only, see 6845, PCjr VGA access)
3DB Clear light pen latch (any write)
3DC Preset Light pen latch
3DF CRT/CPU page register (PCjr only)
3E8-3EF COM3 non PS/2 UART (Reserved by IBM) (see UART)
3F0-3F7 Floppy disk controller (except PCjr)
3F2 controller control port
3F4 controller status register
3F5 data register (write 1-9 byte command, see INT 13)
3F8-3FF COM1 Primary Asynchronous Adapter (see UART)
3220-3227 PS/2 COM3 (see UART)
3228-322F PS/2 COM4 (see UART)
4220-4227 PS/2 COM5 (see UART)
4228-422F PS/2 COM6 (see UART)
5220-5227 PS/2 COM7 (see UART)
5228-522F PS/2 COM8 (see UART) |
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