[Coco] coco3 lowercase pokes!

Arthur Flexser flexser at fiu.edu
Thu Oct 21 12:00:14 EDT 2010

Is that Ram-size bit in $FF22 actually used for anything?  I doubt it.  And
the use of single-bit sound is also pretty rare, so I think it makes no
difference if you don't preserve bits 0-1.  My 2 cents.

On Thu, Oct 21, 2010 at 9:05 AM, Robert Gault <robert.gault at att.net> wrote:

> 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:
>>> 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.
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