Parallel ASCII keyboards

[Allison]

>
>Subject: Re: Parallel ASCII keyboards
>   From: "Ethan Dicks" <ethan.dicks at gmail.com>
>   Date: Fri, 28 Jul 2006 13:16:25 +1200
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 7/28/06, M H Stein <dm561 at torfree.net> wrote:
>> --------------Original Message:
>> From: "Ethan Dicks" <ethan.dicks at gmail.com>
>> Subject: Re: Parallel ASCII keyboards
>>
>> <snip>
>> My recollection is that the mid-1970s were the heyday of ASCII
>> keyboards (AIM-65 and similar machines).
>> <snip>
>> ---------------Reply:
>> ASCII keyboard on an AIM65??? Not on any of mine...
>
>I have to admit that I've never dug into the AIM-65 ROMs, so if not
>ASCII, then just scan codes that get converted in software?
>
>-ethan

A lot of the keyboards were laid out such that the row column values were
ASCII 1:1 corospondence for the the non shifted condition.  Those that
use the Ay, KRO chips this was the rule and also those chips had a ~2500
bit rom to sort out things like shift and alt-chars.  Scan codes are 
a mostly PC invention. Some of the simpler designs like that sold by RS
and SWTP did it all with a few peices of TTL and some diodes. 

Building a parallel interface ASCII keyboard is not that hard.  The only
hard part is finding a suitable keyboard (keyswitches).

I happen to have to keyboards that are not parallel but the serial format
is like that of the PCxt with one variation, the keycodes are direct ASCII.
The onboard 8035 with 2716 did all the work (key scan, encode and serialize).
the same chip with a minor code change could easily do parallel. 

Out on the net there are PIC based code to translate PS2 keyboard to 
ASCII serial and even parallel. 


Allison