HP-41CY re-initialization ROM
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11-03-2019, 08:32 PM
Post: #12
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RE: HP-41CY re-initialization ROM
(11-03-2019 06:29 PM)Jurgen Keller Wrote: W&W did for sure have such a fail-safe mechanism. Unfortunately, I didn't found any information about it. There is also a valued member of this forum who has developed such a re-initialization module in the past. However, he decided to not disclose that module for personal reasons and I fully respect his decision. Nevertheless, for personal curiosity, to get into MCODE-ing and to be able to restore my 41CY when needed, I wanted to solve the mystery. So basically you can just use a page 4 ROM to write an ENROM1 instruction at the last address of the corrupted page which is also stuck in some secondary bank. Then call that address, bank 1 is switched in and execution falls into the next page where you have another ROM of your own, which could be just RTN (or NOP and RTN to make it safer) to pass control back again to page 4. Is that a correct understanding? |
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