[Coco] GIME questions

[Robert Gault]

Robert Gault wrote:
> David Gacke wrote:
> 
>> 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.
> 
> 

OK just so everyone is on the same page, the code in question is from 
the 32K ROM in a Coco3 and is as follows:

  lda #Coco+MMUEN+MC3+MC2+MC1
  sta $$FF90
  leax begmove,pcr
  ldy #$4000
LC02F ldd ,x++
  ldu ,x++
  std ,y++
  stu ,y++
  cmpx #endmove
  bcs LC02F
  jmp $4000

David asked why when stepping through this code, the contents of $4000 = 
that of $C000. He may have meant begmove. Regardless, the content at 
$4000 should be RAM and will look like whatever regY contained after the 
std ,y++.

David, would you clarify what your problem is?