Hello all, >My only opinion is that they use the 6510 as a giant decoder for address >$0001 with build-in I/O. But if this is the case, why not using some, much >cheaper, gates and a latch like the 373 or equivalent? You're right, the 6510 is a decoder for $0001. There are two reasons why you can't use a simple latch: 1. You've got to emulate the behaviour of the DDR at $0000, too. So I has got to be a more sophisticated latch. (I don't know the 373, so I cannot say if it would handle this correctly). 2. The 6510 handles $0000 and $0001 internally, so read and write access cannot be seen from outside. (Well, they can be observed, but the data bus doesn't contain any useful information in this case). That's the main reason why a 6510 is used: It always exe- cutes the same opcode and data as the internal 6510, so any store to $0000 or $0001 is the same as internally, so the on-chip port provides the same information as the one of the internal 6510. >- Next sentence: the external Kernal is located in "abschaltbaren" ROM (= >can be disabled) Except for that line running into the blue, I did not find >a way to disable the external ROM. Well, I have to look if I will find that magazine at home and have a look at it. I remember seeing such a schematic these days, but I don't remember if it was RUN or 64'er... Spiro. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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