[Coco] coco3 lowercase pokes!

[Robert Gault]

Willard Goosey wrote:
> On Wed, Oct 20, 2010 at 09:46:04PM -0500, Little John wrote:
>> Willard, this is what I have been using to accomplish the lowercase:
>> POKE&H95C9,&H10 (without this BASIC will turn lowercase back off) - I
>> noticed you used&H17.
>
> Ahh, then&h95C9 stores what BASIC thinks the IO register should be!
>
> I was reading old Rainbow magazines and stumbled across the pokes.
> Since I already have a history of answering my own questions on the
> list, I posted it. :-)
>
>> I had assembled a table at one time that listed the
>> different effects of different values.. but it's long since been misplaced.
>
> Heh, I still have mine.  Oddly enough I seem to have lost the on-disk
> version though.  A shame, that file was so old it was typed in with a
> hacked version of the BASIC sample program "PRINT OR REVISE".
>
>> and rather than POKE&HFF22,&H10, i was using:
>> POKE&HFF22,PEEK(&HFF22)OR&H10
>> results are the same...
>
> Yes, much better, not clobbering the rest of the register's bits.
>
> Willard

With the addresses in hand, I checked the service manual and Unravelled book. 
So, for an exact description of what the POKEs are doing ....

Extended Basic routine at $95AC-$95CE : "Set the SAM to Alpha mode and zero out 
all except the CSS pin." (Unravelled)  Value sent to $FF22:
  LDA $FF22
  ANDA #%00000111      this value changed by POKE&H95C9
  STA $FF22

That means only RS-232 input, single bit sound, and ram size are preserved and 
the Unravelled comment about CSS is incorrect. To keep upper/lower case, bit-4 
(GM0 & upper/lower case) must be retained. Thus the POKEd value of $17 which 
would also preserve the Case bit. Other effects could be obtained by retaining 
more of the VDG control bits 3-7.

By the way CSS controls the color set.