Hallo Michael, > this has already been done in 64er Sonderheft 10 / 1986. I know, the ISA card I built for my PC was based on this design. But there was an earlier one in 7 / 1985, just for the C64 and based on the 6821. > There is a patched Kernal for C64 and C128 That I didn't know (anymore), I just thought there was a C128 version only. Otherwise I probably had chosen to disassemble these versions. And maybe I still will. > There is a board is based on a 8255. Another reason I chose for the 6821 version is that the 6821 looks more like the 6526. Only during the disassembling I realised I had forgotten about the Control Register construction. But this version came with a BASIC programm that patched the original Kernal. And by changing it a bit, it enabled you just to incorperate the IEEE routines. A file compare enabled me to find out what exactly was changed. The pattern behind the changes was quite simple: the moment the C64 found out it had to make use of the IEC bus, a JMP replaced some original routines. The JMP lead to a routine that first checked whether the use of IEC or IEEE was wanted. If IEC, the replaced code was executed and then C64 jumped back to the rest of the original routines. In this case the new IEEE routines replaced some tape code. And now the weird thing: nothing was done to disable the use of the tape! And the IEEE routines themself weren't that good as well: they simply didn't follow the official IEEE protocol all the time. But at least it gave me the most wanted information: what parts of the Kernal do I have to change. The program only uses the so far unused (AFAIK) zero page address 2. Here you write the number of the IEEE device. If the number of the wanted device is the same as the zero page address, the IEEE routines are executed. Quite simple. And I'm going to add another mechanism: treat everyting above 11 as IEEE. CBM-HD can emulate every number from 8 to 31. So I could even connect a real IEEE drive, if needed. -- ___ / __|__ / / |_/ Groetjes, Ruud Baltissen \ \__|_\ \___| http://Ruud.C64.org De informatie in dit e-mailbericht is vertrouwelijk en uitsluitend bestemd voor de geadresseerde. Wanneer u dit bericht per abuis ontvangt, verzoeken wij u contact op te nemen met de afzender per kerende e-mail. Verder verzoeken wij u in dat geval dit e-mailbericht te vernietigen en de inhoud ervan aan niemand openbaar te maken. Wij aanvaarden geen aansprakelijkheid voor onjuiste, onvolledige dan wel ontijdige overbrenging van de inhoud van een verzonden e-mailbericht, noch voor daarbij overgebrachte virussen. APG Algemene Pensioen Groep NV is gevestigd te Heerlen en is ingeschreven in het handelsregister van de Kamer van Koophandel Limburg onder nummer 14099617 The information contained in this e-mail is confidential and may be privileged. It may be read, copied and used only by the intended recipient. If you have received it in error, please contact the sender immediately by return e-mail; please delete in this case the e-mail and do not disclose its contents to any person. We don't accept liability for any errors, omissions, delays of receipt or viruses in the contents of this message which arise as a result of e-mail transmission. APG Algemene Pensioen Groep NV is registered in the trade register of the Chamber of Commerce Limburg, The Netherlands, registration number: 14099617 Message was sent through the cbm-hackers mailing listReceived on 2012-08-14 07:00:04
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