CONNECTORS
KEYBOARD CONNECTOR
Keyboard connector pin-out is as follows:
PIN
SIGNAL
FUNCTION
1
SPKOUT
Speaker out
2
SPKVCC
Speaker common (+5V)
3
/RESIN
Reset in
4
/RESINGND Reset
common
5
MSCLK
Mouse clock (unsupported)
6
KBCLK
Keyboard clock
7
KBDAT
Keyboard data
8
MSDAT
Mouse data (unsupported)
9
KBGND
Keyboard ground
10
KBVCC
Ke5V
If a keyboard is not used, it is possible to speed up 4C27 boot-up by grounding KBCLK. This informs
the BIOS that no keyboard is present. This avoids the 2-3 second wait for keyboard response to the
reset command.
SERIAL PORT CONNECTOR
P2 and P4 are the serial port connectors. P2 and P4 are 10 pin, dual row .1" headers. The
suggested mating connector is AMP PN 499934-1. This is an IDC (flat cable) type connector.
When the flat cable from P2 or P4 is terminated with a male 9 pin D type connector (suggested
connector AMP 747306-4), the 9 pin connector will have a similar pin-out to the AT type 9 pin serial
port. The pin 10 wire must be stripped from the cable before installing the D connector. A one foot
long serial port adapter cable is available from MESA .
The default BIOS port mapping selects P2 as COM1 and P4 as COM2.
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4C27 CPU USER'S MANUAL