[Coco] GIME questions

[David Gacke]

Hi Guys,

I've got a GIME problem and I'm not sure what's going wrong. For some
reason, "I think", it's not mapping RAM correctly.

I'm stepping thru the startup ROM code on my CoCo 3, which matches the
version I'm looking at in MESS. Just a plain old CoCo3 ROM.

Anyway, there's a write to $FF90 with a value of 0x0A, then there's some
startup code to set palette registers to all green, then there's some
code to start copying code from $C03F to $4000.

This is where I get into trouble. Immediately after writing the first
word, with the STD, Y++ instruction, I read back the contents. The
address I'm reading from is $4000 and I'm seeing the same data that is
at $C000.

For some reason, it didn't get $4000 mapped correctly, it is still
pointing to ROM. Also, are there any special conditions I should be
aware of when writing these GIME registers, like wait states, etc.

Any help would be GREATLY appreciated.  :)



Dave Gacke


Oh! As a side note, I've verified the data and addresses are correct
with a scope, so at least my wiring is good!