# ISA

ISA=Industry Standard Architecture

(at the card)
(at the computer)

62+36 PIN EDGE CONNECTOR MALE at the card.
62+36 PIN EDGE CONNECTOR FEMALE at the computer.

Pin | Name | Dir | Description
--- | --- | --- | ---
A1 | /I/O CH CK |  | I/O channel check; active low=parity error
A2 | D7 |  | Data bit 7
A3 | D6 |  | Data bit 6
A4 | D5 |  | Data bit 5
A5 | D4 |  | Data bit 4
A6 | D3 |  | Data bit 3
A7 | D2 |  | Data bit 2
A8 | D1 |  | Data bit 1
A9 | D0 |  | Data bit 0
A10 | I/O CH RDY |  | I/O Channel ready, pulled low to lengthen memory cycles
A11 | AEN |  | Address enable; active high when DMA controls bus
A12 | A19 |  | Address bit 19
A13 | A18 |  | Address bit 18
A14 | A17 |  | Address bit 17
A15 | A16 |  | Address bit 16
A16 | A15 |  | Address bit 15
A17 | A14 |  | Address bit 14
A18 | A13 |  | Address bit 13
A19 | A12 |  | Address bit 12
A20 | A11 |  | Address bit 11
A21 | A10 |  | Address bit 10
A22 | A9 |  | Address bit 9
A23 | A8 |  | Address bit 8
A24 | A7 |  | Address bit 7
A25 | A6 |  | Address bit 6
A26 | A5 |  | Address bit 5
A27 | A4 |  | Address bit 4
A28 | A3 |  | Address bit 3
A29 | A2 |  | Address bit 2
A30 | A1 |  | Address bit 1
A31 | A0 |  | Address bit 0
B1 | GND |  | Ground
B2 | RESET |  | Active high to reset or initialize system logic
B3 | +5V |  | +5 VDC
B4 | IRQ2 |  | Interrupt Request 2
B5 | -5VDC |  | -5 VDC
B6 | DRQ2 |  | DMA Request 2
B7 | -12VDC |  | -12 VDC
B8 | /NOWS |  | No WaitState
B9 | +12VDC |  | +12 VDC
B10 | GND |  | Ground
B11 | /SMEMW |  | System Memory Write
B12 | /SMEMR |  | System Memory Read
B13 | /IOW |  | I/O Write
B14 | /IOR |  | I/O Read
B15 | /DACK3 |  | DMA Acknowledge 3
B16 | DRQ3 |  | DMA Request 3
B17 | /DACK1 |  | DMA Acknowledge 1
B18 | DRQ1 |  | DMA Request 1
B19 | /REFRESH |  | Refresh
B20 | CLOCK |  | System Clock (67 ns, 8-8.33 MHz, 50% duty cycle)
B21 | IRQ7 |  | Interrupt Request 7
B22 | IRQ6 |  | Interrupt Request 6
B23 | IRQ5 |  | Interrupt Request 5
B24 | IRQ4 |  | Interrupt Request 4
B25 | IRQ3 |  | Interrupt Request 3
B26 | /DACK2 |  | DMA Acknowledge 2
B27 | T/C |  | Terminal count; pulses high when DMA term. count reached
B28 | ALE |  | Address Latch Enable
B29 | +5V |  | +5 VDC
B30 | OSC |  | High-speed Clock (70 ns, 14.31818 MHz, 50% duty cycle)
B31 | GND |  | Ground
C1 | SBHE |  | System bus high enable (data available on SD8-15)
C2 | LA23 |  | Address bit 23
C3 | LA22 |  | Address bit 22
C4 | LA21 |  | Address bit 21
C5 | LA20 |  | Address bit 20
C6 | LA18 |  | Address bit 19
C7 | LA17 |  | Address bit 18
C8 | LA16 |  | Address bit 17
C9 | /MEMR |  | Memory Read (Active on all memory read cycles)
C10 | /MEMW |  | Memory Write (Active on all memory write cycles)
C11 | SD08 |  | Data bit 8
C12 | SD09 |  | Data bit 9
C13 | SD10 |  | Data bit 10
C14 | SD11 |  | Data bit 11
C15 | SD12 |  | Data bit 12
C16 | SD13 |  | Data bit 13
C17 | SD14 |  | Data bit 14
C18 | SD15 |  | Data bit 15
D1 | /MEMCS16 |  | Memory 16-bit chip select (1 wait, 16-bit memory cycle)
D2 | /IOCS16 |  | I/O 16-bit chip select (1 wait, 16-bit I/O cycle)
D3 | IRQ10 |  | Interrupt Request 10
D4 | IRQ11 |  | Interrupt Request 11
D5 | IRQ12 |  | Interrupt Request 12
D6 | IRQ15 |  | Interrupt Request 15
D7 | IRQ14 |  | Interrupt Request 14
D8 | /DACK0 |  | DMA Acknowledge 0
D9 | DRQ0 |  | DMA Request 0
D10 | /DACK5 |  | DMA Acknowledge 5
D11 | DRQ5 |  | DMA Request 5
D12 | /DACK6 |  | DMA Acknowledge 6
D13 | DRQ6 |  | DMA Request 6
D14 | /DACK7 |  | DMA Acknowledge 7
D15 | DRQ7 |  | DMA Request 7
D16 | +5 V |  |
D17 | /MASTER |  | Used with DRQ to gain control of system
D18 | GND |  | Ground

Note: Direction is Motherboard relative ISA-Cards.

Note: B8 was /CARD SLCDTD on the XT. Card selected, activated by cards in XT's slot J8

Contributor: | Joakim Ögren, Rob Gill

Source: | IBM PC/AT Technical Reference, pages 1-25 through 1-37
| comp.sys.ibm.pc.hardware.* FAQ Part 4 - maintained by Ralph Valentino

Copyright © The Hardware Book Team 1996-2004.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2002-01-10