Re: 6809 / 6702 puzzle

On Sun 05 Feb 2012 at 12:34:47 +0100, A.Fachat wrote:
> I looked it up in the schematics, the dongle should be reachable from
> the 6502 side, so it should be easier for us 6502 guys to test it,
> compared to having to write 6809 code :-)

That helps, since I don't have the 6809 assembler going yet in VICEs
monitor, and the Waterloo monitor doesn't have one either (only
disassembly).

Things that are likely to be of interest, are such as
- if you read out the location multiple times, do you get the same
  result, or does it vary?
- if you wait longer before you read, do you still get the same value,
  or does it vary? In other words, does it depend on timing?

Here is a super simplistic test for the first item:

(C:$101e) d 1000
.C:1000  A9 00       LDA #$00
.C:1002  8D E0 EF    STA $EFE0
.C:1005  AD E0 EF    LDA $EFE0
.C:1008  8D 00 20    STA $2000
.C:100b  AD E0 EF    LDA $EFE0
.C:100e  8D 01 20    STA $2001
.C:1011  AD E0 EF    LDA $EFE0
.C:1014  8D 02 20    STA $2002
.C:1017  AD E0 EF    LDA $EFE0
.C:101a  8D 03 20    STA $2003
.C:101d  00          BRK

For a simple test of question 2, stuff a bunch of NOPs between the store
and the loads:

(C:$1029) d 1000
.C:1000  A9 00       LDA #$00
.C:1002  8D E0 EF    STA $EFE0
.C:1005  EA          NOP
.C:1006  EA          NOP
.C:1007  EA          NOP
.C:1008  EA          NOP
.C:1009  EA          NOP
.C:100a  EA          NOP
.C:100b  EA          NOP
.C:100c  EA          NOP
.C:100d  EA          NOP
.C:100e  EA          NOP
.C:100f  EA          NOP
.C:1010  AD E0 EF    LDA $EFE0
.C:1013  8D 00 20    STA $2000
.C:1016  AD E0 EF    LDA $EFE0
.C:1019  8D 01 20    STA $2001
.C:101c  AD E0 EF    LDA $EFE0
.C:101f  8D 02 20    STA $2002
.C:1022  AD E0 EF    LDA $EFE0
.C:1025  8D 03 20    STA $2003
.C:1028  00          BRK

Of course they are just extremely simple cases, even if both tests result
in always the same output that doesn't prove that later reads will be
the same.

> André
-Olaf.
-- 
___ Olaf 'Rhialto' Seibert  -- There's no point being grown-up if you 
\X/ rhialto/at/xs4all.nl    -- can't be childish sometimes. -The 4th Doctor

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