Hallo Ruud (and thanks!) >2) "controlled by a line from the peripheral" I'm not sure what you mean, an >external signal controls wether the data is outputted or not like a 541 or >245? If that is what you mean then: no, the 6522 is not able to do that. But >IIRC, the 8255 cannot either. The 8255 in mode 2 allows port A to be in bi-directional mode, that is to output data when signalled by the Peripheral where as it normally has the lines in input mode (to avoid bus contentions). Did I understand mode 2 incorrectly? >3) on FUNET you'll find some docs on the 6522 that can tell you if the >a doc mentioning this bug. (or am I wrong, Marko ?) None of the documents I've read describe the "shift" bug, though I have heard of it. It would be good to know what it exactly is (will save pulling out many hairs at a later stage!) > Is either chip more attractive from a C64 interfacing point of view? The 8255 has 24 I/O lines, the 6522 ~20. But the ones of the 6522 can progammed individual, the ones of the 8255 only in blocks of 4 or 8. Remark: nasty habbit of the 8255, reprogramming the direction of a block resets all outputs :( >the 6522 a 74 due to the timing Can you describe this? Aren't all 65xx chips bus /timing compatible? Regards, Nick PLEASE TAKE NOTE: The contents of this email (including any attachments) may be privileged and confidential. Any unauthorised use of the contents is expressly prohibited. If you have received this email in error, please advise us immediately (you can contact us by telephone on +61 8 9441 2311 by reverse charge) and then permanently delete this email together with any attachments. We appreciate your co-operation. Whilst Orbital endeavours to take reasonable care to ensure that this email and any attachments are free from viruses or other defects, Orbital does not represent or warrant that such is explicitly the case (C) 2000: Orbital Engine Company (Australia) PTY LTD and its affiliates Message was sent through the cbm-hackers mailing list
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