[Coco] 6809 example

[Roger Taylor]

At 02:52 AM 1/19/2004 -0500, you wrote:

>No, as I've been implying, it does not make sense to change the fcc 
>statement. And yes, there are lowercase letters on the Coco. Some Coco2 
>units have true lowercase in low res and the Coco3 has true lowercase in 
>low res. To take advantage of true lowercase you need to learn something 
>about the Coco hardware in addition to learning assembly language as there 
>is not direct support in the ROMs. To take advantage of the built-in OS, 
>Basic or OS-9, you need to learn the specifics of the OS which is hard to 
>do before you are proficient in assembly. Can you say "catch-22"?
>
>Even without using the CHROUT ROM hook, only a few lines are needed to 
>change your code loop to a generic form that will handle some punctuation, 
>numbers, and both upper and lowercase letters. If I don't see an answer in 
>a day or so, I'll post a version.

On the CoCo 3, or in ALL-RAM mode on a 26-3134B CoCo 2 (probably other 
models as well), you can do the following to keep the 32x16 VDG lowercase 
mode enabled.

To patch the BASIC ROM to enable true lowercase letters in the 
standard/stock 32-column mode:

POKE 38344,134
POKE 38345,16

Or my favorite:

POKE 38344,134
POKE 38345,85   (no black border, resembles the 40-wide screen)

The code you are patching is part of a routine in BASIC:

LDA 65314
ANDA #7   <----
STA 65314

This code is called all the time from BASIC to reset back to the stock VDG 
mode.  So if you patch that routine, BASIC will make sure your own custom 
mode is used, instead.


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Roger Taylor