[sebhc] HASL-8 Bug/Corruption?

Dave Dunfield dave04a at dunfield.com
Wed May 12 17:27:55 CDT 2004

At 15:52 12/05/2004 +0000, you wrote:
>>So .. it looks like there's either a bug in HASL-8, or my copy of it is
>Wow .. it sure sounds corrupted.  I wonder how these files were created, 
>since the CRC at the end of the file is good.  Anyone know?

Well... A: I didn't check the CRC - I just clipped the code out of the PID
file and loaded it into the emulator, and B: The PID file was probably created
by someone who loaded the tape and then saved it - if it was corrupted in memory
between these two events, it would have been saved with a correct CRC (for the
incorrect code), so I think that it's possible that it has been corrupted.

>On the off chance that is really is a bug, it would have to be one that was 
>not apparent on the H8.  Can you set your emulator to ignore an 
>unimplemented code and keep running like a real 8080 would?  See if the 
>software happens to "work" in that case.

I've added a '/I' option to Ignore bad opcoes, and the program does appear to
work, however you can't always just Ignore a bad opcode - due to imcomplete
decoding in the 8080, some "bad" opcodes behave just like other valid opcodes
(which do something) - $20 (040) is "lucky" in that it decodes to a NOP, so
it doesn't matter.

My favorite use of this was I once modified my assembler to output $DD for all
CALL instructions - worked fine on my 8080 which decodes it as a CALL, however
it drove a friend with a Z80 nuts!

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Vintage computing equipment collector.

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