Exar 22-908-03 anyone ?

From: Jos Dreesen <jos.mar_at_bluewin.ch>
Date: Mon May 31 00:46:23 2004

Tony Duell heeft op maandag, 31 mei 2004 om 02:28 (Europe/Zurich) het
volgende geschreven:
>> It took out the 8035, a 74ls373 and, much worse, an unknown to me Exar
>> IC 22-908-03, datecode 1983
>
> How many pins does this have?

It is a 20 pin IC and it sits at the receiving end of the keyboard
matrix, the other side of the matrix is driven by two 74138.

>
> THis sounds a lot like one of the 2 semi-custom ICs used with a
> Keytronics capacitive keyboard. I've seen 22-908-3B and 22-950-3B used
> in
> the PERQ 2 series and elsewhere. They have 20 pins each. The former is
> the (latching) sense amplifier between the 8 keyboard row lines and an
> 8
> bit input on the microcontroller.

It seems to be the exact same IC. The keyboard is indeed a Keytronics.
>
> You might be able to get a replacement for these from another
> Keytronics
> keyboard (e.g. a PC one).
I'l start looking around..
>
>
> I should be able to find pinouts for the PERQ keyboard ICs.
I was hoping to kludge a replacement with some TTL's, but this might be
difficult with a capacitive coupled keyboard.

>
> Incidentally, I assume there's an EPROM in the keyboard (The 8035 has
> no
> internal ROM, the '373 sounds like an address latch). Did this survive?

The '373 was indeed the addresslatch for the 8035. The eprom (I do have
an image) seems to have survived OK, since after replacement of both IC
I see the scanning signals on the driver side of the matrix, which
weren't there before.

Thanks for all input, Jos
Received on Mon May 31 2004 - 00:46:23 BST