But how to do it? A first look at Vicmon's memory shows no readable opcode list. Does somebody has any idea? Maybe Vicmon guru Mike?
Pimping up Vicmon to read illegal opcodes
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Pimping up Vicmon to read illegal opcodes
Hello dudes! Sometimes it could be nice to tell Vicmon to show the translation of illegal opcodes like HLT ($ 02) and so on.
But how to do it? A first look at Vicmon's memory shows no readable opcode list. Does somebody has any idea? Maybe Vicmon guru Mike?
But how to do it? A first look at Vicmon's memory shows no readable opcode list. Does somebody has any idea? Maybe Vicmon guru Mike?
Valid rule today as earlier: 1 Byte = 8 Bits
-._/classes instead of masses\_.-
-._/classes instead of masses\_.-
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Mike
- Herr VC
- Posts: 4901
- Joined: Wed Dec 01, 2004 1:57 pm
- Location: Munich, Germany
- Occupation: electrical engineer
Re: Pimping up Vicmon to read illegal opcodes
Indeed I know how the opcode decode and encode of VICMON works. It is done by a standard algorithm originally devised by Steve Wozniak and which has been reproduced in many contemporary debuggers/monitors.
Some years ago we had a discussion here in Denial about the undocumented instructions present in the NMOS line of 65xx CPUs. Neither BASIC nor KERNAL employ these and their use is rather limited, save for the odd cycle or byte saved in a few circumstances.
IMO, extending VICMON with said feature is like barking up the wrong tree. Some rather blatant bugs and annoyances in VICMON should be fixed first.
I mainly chose VICMON for my primer series, as it's one of the most widespread monitors around for VIC-20. But the techniques presented there transfer without any issues to other monitors like HESMON or my own MINIMON.
Some years ago we had a discussion here in Denial about the undocumented instructions present in the NMOS line of 65xx CPUs. Neither BASIC nor KERNAL employ these and their use is rather limited, save for the odd cycle or byte saved in a few circumstances.
IMO, extending VICMON with said feature is like barking up the wrong tree. Some rather blatant bugs and annoyances in VICMON should be fixed first.
I mainly chose VICMON for my primer series, as it's one of the most widespread monitors around for VIC-20. But the techniques presented there transfer without any issues to other monitors like HESMON or my own MINIMON.