Date: 2007-12-13 07:22:11
Hallo Jim, > You are correct, of course, and it's trivial to change it. However, it > does make the memory map funky: > > $00-$1f=IDE registers low byte > $20-$3f=IDE registers hi byte Nope, A5 is just needed to read/write the High byte of the data ie. D8..D15. Have a look at IC7A, the first half of a 139, you will see that both A5 and R/W are responsible for selecting the 573's. In fact only the addresses $20 and $30 are used, the rest are mirrors of those two addresses. What does $30 you may ask? If you have a look at IC7B, the second half of the 139, A5=1 makes it to output (H)'s only, thus disabling the interfaces. Yes, interface_s_ as this 139 also enables you to connect a second IDE interface to the, at this moment, not used outputs Y2 and Y3! If you don't want two interfaces, connect A4 to the CS of this 139 and input 3 of the other half. Regarding the 8250 discussion. IMHO it is possible to alter the decoding scheme of a CBM in such a way that all the I/O still appears at the original addresses but won't be mirrored anymore, thus freeing enough space for our own purposes. IMHO a 74LS154 will do the trick. But, as said before, Jack started the discussion mentioning the 8250: see the subject. Nice idea but I forsee one problem: are there any well documented sources available? I have them of the 8050 but I already found out that the ROMs of the FDC's of the 805 and 8250 are quite different. If it was up to me, I would start in the same way as I did with the 1541: soldering the interface and trying to make this work first only using a BASIC program. My question: is it possible to force a program up on the FDC of an IEEE drive ???? That I really would like to know! The IEEE drives have a big advantage: a sepperate FDC. IMHO this means we can adjust the ROM so the FDC is able to handle an harddisk without having to alter the software for the other 6502. Remark: don't forget that the ROM for this 6502 contains some routines meant for the FDC. -- ___ / __|__ / / |_/ Groetjes, Ruud \ \__|_\ \___| 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. Stichting Pensioenfonds ABP is gevestigd te Heerlen en ingeschreven bij de Kamer van Koophandel Zuid Limburg onder nummer: 41074000 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. Stichting Pensioenfonds ABP, having its registered office at Heerlen, is registered in the Traderegister of the Chamber of Commerce Zuid Limburg (Maastricht), the Netherlands, registration number: 41074000 Message was sent through the cbm-hackers mailing list
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