For posterity, I figured I would post some info uncovered on the UNIX PC keyboard. There is a 6850 ACIA on the motherboard which communicates via serial (1200 baud N81) to the keyboard controller which I believe is a MCS-48 microcontroller. My keyboard
has a Signetics CP8038 @ 11 MHz, also labeled "80-552871". I was able to find a similar Cortron keyboard for a Burroughs B25 aka NGEN (
https://deskthority.net/viewtopic.php?t=12757) that uses a Toshiba 8049 @ 11 MHz, also labeled "80-552871". This leads
me to believe the Signetics CP8038 is also an 8049. The 8049 has 2K of ROM, 128 bytes RAM, and 27 I/O ports. The protocol from the keyboard to the 6850 involves injecting some additional characters such as KBD_BEGIN ('0xDF'), MOUSE_BEGIN ('0xCE'), KBD_
ALL_UP ('0x40') after no more keys depressed, or the high bit set in a keycode to indicate it's the last character being sent. The 8049 must be responsible for reading data from the mouse (which uses a 6805 @ 4 MHz) and injecting the mouse data within
the protocol. The 8049 also receives commands from the 6850 such as reset ('0x92'), turn on/off CAPS LOCK or NUM LOCK LED. (sidenote: 8038 is also a MCS-48 chip, but it has no ROM, so I doubt this is the proper label on the Signetics chip)
Thanks for Phil and AJ, without them I would have little to no knowledge of this.
Jesse
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