Re: 65816/GS - move SHGR memory?

[gids.rs@sasktel.net]

On Thursday, November 8, 2012 9:53:46 AM UTC-6, Steve Nickolas wrote:
> I'm trying to tweak a program that uses the SHGR screen to display a test 
> image on a GS (otherwise doesn't require a GS).
> My old attempts to tweak the SHGR screen have been unreliable as I was 
> using some assumptions about bankswitching that may or may not be true to 
> access SHGR mode without switching to 65816 mode.  I don't know anything 
> about 65816, honestly, though I have the ability to assemble 65816 code.
BTW, is it possible that the SHGR image on the existing crack of MECC 
> "Computer Inspector" is messed up?  (This is the program in question.)


to access the SHR screen, do you mean to view or edit the screen

To view the SHR screen, the code is as simple as

LDA #$80
TSB $C029  ; TURN ON SHR
JSR FDOC  ; WAIT FOR KEYPRESS
LDA #$80
TRB $C029  ; TURN OFF SHR


to edit the SHR screen, I found it easier to turn on shadowing and draw in bank 1, than to fiddle with the $E1 bank

But I found out with trial and error that the color palettes have to be stored in bank $E1 before the shadowing worked.

Rob