[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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