I am looking for information about undocumented instructions for the MC6800. I created a table based on the December 1977 issue of BYTE magazine and information from Japanese computer magazines, but there are still some unclear points. Is there any other information? Thank you.
This isn’t a serious or helpful suggestion, but in principle you could explore all opcodes using a transistor level simulation like Visual 6800 in JavaScript
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HCF could be a interesting simulation, as to just what it does and how to reset the cpu.
Nice one! Here’s an alternative
Thank you for reply.
Is there no documentation (magazines or books) on the 6800’s undefined instructions like BYTE magazine?
Of course, I’m checking on visual6800, but any documentation would be helpful.
maybe some help here
Also from here we read
You can read about the Undocumented M6800 Instructions in this article from BYTE Magazine, or in the article Investigating the HCF (Halt & Catch Fire) instruction on Motorola 6800.
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Here’s a working link to the BYTE article:
Undocumented 6800 Instructions " by Gerry Wheeler, page 46, December. 1977 BYTE
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Another download site
https://vintageapple.org/byte/