The way I understand it the UI- command (if required) must be issued once per diskdrive reset, including the sending of UI and UJ commands. It's a bit like the software "re-numbering" of drives which is forgotten once a UI is issues (a real pain!!). Hence, its possible that the Forth program issues a UI and clears the setting... The UI- command sets Tv =20us (1540 default) instead of Tv=60-70us (which is the 1541 default). The Tv (time data is valid) signal was lengthened with the introduction of the C64 which has bad-lines lasting up to 43us and hence may hang if it missed reading the signal in time.... Interestingly you can use the faster speed with UI- if you blank the screen on the C64/128 before doing the disk I/O. Whether you need to use UI- with a VIC20 or not I would question. My PAL set up works with the 1541/1571 without changing the setting. In theory it is no problem as the VIC20 does its job and waits for the the clock line to toggle back. - Nick > -----Original Message----- > From: Marko Mäkelä [SMTP:email@example.com] > Sent: Wednesday, 15 November 2000 18:20 > To: firstname.lastname@example.org > Subject: CBM 1541 (fwd) > > Dear John, > > Since I'm buried under work at the moment, I'm forwarding your question to > the cbm-hackers mailing list. (Note: when replying to the message, be > sure to send a CC to John.) > > I have never required the UI- or UI+ commands, but your situation could be > different, since the PAL VIC-20 runs at 1.108 MHz while the NTSC VIC-20 > runs at 1.023 MHz. The PAL C64 is much more slower than the PAL VIC-20: > 0.985 MHz minus the cycles stolen by the VIC-II. The NTSC C64 runs at > 1.023 MHz. The drive runs at 1 MHz in any case. > > I'd rather suspect some kind of a hardware problem. The UI-/UI+ setting > is definitely not written on the disk; it just alters some delays in the > drive's serial bus protocol. > > Marko > > ---------- Forwarded message ---------- > Date: Tue, 14 Nov 2000 13:40:59 -0800 > From: "Kotrba, John" <KOTRBJO@mail.northgrum.com> > To: "'Marko.Makela@HUT.FI'" <Marko.Makela@HUT.FI> > Cc: 'home' <email@example.com> > Subject: CBM 1541 > > Marko; > > I see you have considerable interest in details of old CBM equipment. > Maybe > you can advise me since I see you provided a disassembly of 1541 ROM. I > am > using a 1541 drive with my VIC-20, operating BASIC and FORTH (Datatronic > v1.1). The owner's guide for 1541 refers to "matching drive to computer" > by > sending "UI-" to control channel if VIC and "UI+" if C64 computer. I have > found I need to do this reading BASIC program files, else drive spins > without finding program. When I use FORTH (ramdom file format), it seems > that it I forget to send command "UI-" command, my disc reads fine > (written > previously on same drive). Now I may have used that command possibly when > I > first wrote to that disc, but not now. However, I'm making a new system > disc and having trouble getting it to write to a newly formatted disc. > Now > I'm wondering it this is because I got used to not sending the UI- and > this > is how its showing up. I guess my question is: should that command be > manditory anytime disc is used, or is it possible its needed when first > creating disc and then accomodates even if not sent? Also, might the > nature > of file system eg sequential program vs ramdom blocks matter. I > eventually > find answers to these type of questions experimentally, but its a big > waste > of time. I'm currently trying to create several FORTH system discs for > backup purposes so I don't have an accident and loose much effort. I can > only devote so much time to a hobby! > > > Your opinion? > > > > John Kotrba > > - > This message was sent through the cbm-hackers mailing list. > To unsubscribe: echo unsubscribe | mail > firstname.lastname@example.org. 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 are free from computer viruses or other defects. (C) 2000: Orbital Engine Company (Australia) PTY LTD and its affiliates - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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