On Thu, 18 Nov 1999 email@example.com wrote: > The make sure evrything goes smooth, you put some NOPs behind the > instruction in case the timing is not quit right. I have never understood this. I've seen unnecessary NOPs in the bank switching code of cartridges and in some other places. It is hard to believe that there could exist a latch having a long enough propagation delay (over 300 ns) for an approach without any NOPs to fail. > The Z80 starts at $0000, its reset-address, the first time it is > activated. The rest is the same as with the 6510. According to the Programmer's Reference Guide, in the Commodore CP/M cartridge, the Z80 addresses do not directly correspond to 6510 addresses. I think it was off by $1000 ($1000 in the C64 memory would be $0000 in the Z80 address space). > I did not completely understand the above. I did. He is planning to use the C64 for I/O of another computer system (this is just what accelerator cartridges do). One Finnish guy asked about this in comp.sys.cbm recently; maybe you could co-operate with him? I think it's quite possible to use the cartridge port for write-only access to all of the RAM (maybe expect $d000-$dfff) and I/O. By default, all other memory areas expect $d000-$dfff are write-through (when you write, the value will go into RAM), and by using the -GAME and -EXROM lines appropriately, you could perhaps be able to enable the RAM at $d000-$dfff for writing. Add a wire running into the 6510's CHAREN output, if you cannot figure out any better solution. Marko - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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