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| From: Crown (all posts)
Date: 1998-07-07
Subject: Re: $FD20 - $FD2F
|
Hi there,
>me that the F0 pin of the PLA might be the decoded $FD2x output.
Unfortunately I
>haven't got access to a 264 machine at the moment to try out this theory.
>
>The original plan for the 264 series included a 364 computer, which was to have
>a built-in speech synthesizer. Perhaps this was mapped into $FD20 - $FD2F,
and
>the PLA designed before the 364 was scrapped. If so, then F0 is spare on all
>production 264 series machines, and could be used for something else. Any ideas?
Yes, one of docs I have on the PLA, points towards this. Also on the C16
schematics, in the docs which came with my C16 this line has the name SCS
, which might be decyphered as Speech Chip Select... The Plus4 schematics simply forgots to mention this line.
If you have read carefully that doc you mention, than you know that
$fd20 is written in the RESET process. It's happening at address $CFA6,
first the value $09 is written, then $89 is written to $fd20. So if someone decides to use this address space, be aware of this.
Tibor Biczo / Crown of GOTU
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