[Coco] "Reading" non-readable bytes with PEEK vs ZBUG
robert.gault at worldnet.att.net
Tue Jan 29 19:01:11 EST 2008
Roger Taylor wrote:
> At 07:31 AM 1/26/2008, you wrote:
>> Roger Taylor wrote:
>>> At 07:38 AM 1/25/2008, you wrote:
>>>> There is another approach which will be independent of memory but
>>>> not relocated DOS code. Write a Basic program as a LOADM routine for
>>>> your binary program.
>>>> 10 A=PEEK(&HC003)
>>>> 20 IF A=8 THEN POKE&HD008,&H21 ELSE POKE&HCF2C,&H21
>>>> 30 LOADM"ROGER.BIN"
>>> I now see that you're checking a byte first. I didn't notice that
>>> earlier, sorry.
>> Also I goofed when writing this short piece of code. I intended a BRA
>> to replace the BEQ but used the value for BRN, duh.
>> The POKE value should be &H20 to get the BRA.
> What is the other ROM version you're patching? DECB 2.1 looks like the
> A=8 condition, for sure.
Right, line 20 should read
20 IF A=8 THEN POKE &HD008, &H20 ELSE POKE &HCF2C, &H20
That will be for DOS1.1 A=8 and DOS1.0 A=4. Far as I know this test will
work with other third party DOS but you should check with Art about his
software. What is important is that the BEQ verification test is at the
indicated locations. Oh, and don't worry about the DECB2.x as the 2 just
means Coco3 not a change in DOS.
RGBDOS and therefore HDBDOS should also be covered.
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