silverdr_at_wfmh.org.pl
Date: 2008-11-12 01:08:46
On 2008-11-11, at 23:03, silverdr@wfmh.org.pl wrote: > 3. Sure, but 1) see above, and 2) isn't it much more fun to push > reset with a key combination [...] > and choose one from the menu at will?! Hm, that I guess would require somewhat different approach than what was written by Jim. It would have to blend itself in at top of the address space, release RESET and execute some target machine code before doing the second reset rather than "holding the machine in RESET state" but this is not impossible, right? 1. At RESET, the utility code is put over last pages and uses the 6502 vectors for start, after checking and setting the flag for [4.] 2. It checks the ports for the key combo and upon finding presents the menu. Otherwise proceeds with default KERNAL. 3. the KERNAL image is selected and the utility code communicates with the uC (this possibility is supposed to be there anyway), sending it appropriate data about the choice and triggering the second phase Now: 4. The second phase pulls RESET one more time (and while "holding the machine in RESET state" clears a flag or something so that it doesn't go back to [1.] and RESET endlessly nor skips the menu all the time) 5. Chosen KERNAL is blended-in and RESET is de-asserted. Does that make sense at all? Regards, P. Message was sent through the cbm-hackers mailing list
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