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PC Hardware in a Nutshell, 3rd Edition
book

PC Hardware in a Nutshell, 3rd Edition

by Robert Bruce Thompson, Barbara Fritchman Thompson
July 2003
Beginner to intermediate content levelBeginner to intermediate
874 pages
38h 13m
English
O'Reilly Media, Inc.
Content preview from PC Hardware in a Nutshell, 3rd Edition

PS/2 Keyboard Interface

The PS/2 keyboard interface was introduced with the IBM PS/2 series in 1986, and is now used by all ATX and ATX-variant motherboards. PS/2 keyboards use the 6-pin mini-DIN connector (female at the PC), shown in Figure 19-2 and whose pinouts are described in Table 19-2. On the PC side, the PS/2 keyboard uses the same Intel 8042 or equivalent interface chip as the AT keyboard, which is also assigned IRQ1 and I/O base address 0060.

The PS/2 keyboard connector

Figure 19-2. The PS/2 keyboard connector

Table 19-2. PS/2 keyboard interface signals and pinout

Pin

Signal name

Description

1

DATA

Keyboard data

2

RESERVED

No connection

3

GROUND

Signal ground

4

VCC

+5VDC

5

CLOCK

Keyboard clock

6

RESERVED

No connection

Shield

-

Ground

The AT and PS/2 keyboard interfaces use incompatible connectors, but are electrically and functionally identical. You can connect an AT keyboard to a PS/2 keyboard port or vice versa by building or buying an adapter that uses the pinouts listed in Table 19-3. Many new keyboards come with an adapter to allow their use with the other style connector. Such adapters can also be purchased at most computer stores.

Table 19-3. Pinouts for an AT-to-PS/2 or PS/2-to-AT adapter

PS/2 pin

AT pin

Description

1

2

Keyboard data

2

3

No connection

3

4

Signal ground

4

5

+5VDC

5

1

Keyboard clock

6

-

No connection

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Publisher Resources

ISBN: 059600513XErrata Page