On Wed, 11 Jun 2014, Gerrit Heitsch wrote: > External test equipment can use this feature to test internal CPU > logic and I/O. A program can be loaded into RAM allowing the contents > of the instruction ROM to be dumped to any port for external > verification. To me that -- optimistically -- confirms the "ROM-only" theory, although admittedly the wording is very vague. The ROM-only approach makes things the easiest -- only ROM reads appear outside, program calling in RAM does not require external synchronization with regard to dropping reset to 5V, and you would have even full control over the I/O ports so that e.g. you could run a RAM test and I/O test first before tapping in the ROM read-out routine. > But that might mean that you can only _write_ to any register, but any > read (RAM, ROM, I/O) will only happen from port PC. Unfortunatly, the > data sheet doesn't supply any more details but the term 'all memory > fetches' suggests this being the case. Otherwise I would expect it to > read 'all ROM fetches'. I'm already suprised to see the "apply 10V to reset" hint there. Usually, such information is not publicly disclosed. > To really know what's going on one would need a die shot. Or be brave :) Not sure, how much /1 supply there's left, though. As time allows, I'll try my luck with the 6500/11 I have ... In that very case I might even be able to see the external memory strobe come to life (which the /1 doesn't have). Rainer Message was sent through the cbm-hackers mailing listReceived on 2014-06-11 16:00:04
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