[Coco] "Reading" non-readable bytes with PEEK vs ZBUG
Roger Taylor
operator at coco3.com
Tue Jan 22 12:48:34 EST 2008
At 11:37 AM 1/22/2008, you wrote:
>On 22 Jan 2008 at 7:56, Robert Gault wrote:
>
> > The last message in the original thread suggested that ZBUG (or
> > EDTASM) might have introduced errors in reading non or partially
> > readable bytes such as the MMUs. That does not seem to be the case as
> > you can see from the following test.
> >
> > Source code
> > org $E00
> > rmb 2
> > start ldx #$FFA0
> > E6 00 ldb 0,x
> > A6 84 lda ,x
> > FD 0E 00 std $E00
> > rts
> > end start
> >
> > This was assembled and run from Basic, not used under EDTASM control.
> >
> > Results
> > ?PEEK(&HE00)
> > 248 ie. $F8
> > ?PEEK(&HE01)
> > 56 ie. $38
> >
> > Source code #2
It seems also that an on-the-fly 1-byte patch of LOADM (by LOADM) to
replace the $00 operand with $84 for the MMU register peek would save
me time from adding $40 to the expected peek value. Either way, I
think it'll work beautifully.
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