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Re: Coding for IIgs 2 - working on screen memory





On Thu, 25 Dec 2008, Charlie wrote:

I've never done it that way but it looks like it should work.  Since it
doesn't I would have to look at the bit opcode.  Somewhere in the back of my
mind I think $C005 requires a write (someone else jump in if I'm wrong).

Another remote possibility:  Are you in emulation mode (65816 emulation bit
set)?  If not and the data bank register is set to $00 maybe that over-rides
the $C005 softswitch.  Again my memory cells aren't what they used to be and
I might be way off base.

I never exit 65C02 mode. I entered the code with a CALL from BASIC and that's all pure 6502 (not even 'C02).

BIT does a read access, but nothing goes into any of the registers, I've seen BIT $C010 used a lot.

-uso.