1541 DriveMirror (was Re: Wanted: ultra-rare Commodore 64 stuff)
ethan.dicks at usap.gov
Tue Jan 1 05:18:05 CST 2008
On Tue, Jan 01, 2008 at 03:37:44AM -0600, Jim Brain wrote:
> Dan Gahlinger wrote:
> >I'm looking for something very rare on the commodore 64 (c64 or 64c) line
> >of computers,
> >it was called "drive mirror" for the 1541 disk drives
> >it was basically an LCD display built into the drive that showed the track
> >and sector values.
LCD? I remember an LED track-only display.
> >I read a magazine article (or online) once that showed how to do the track
> >and sector displays...
Any recollection where?
> I'm assuming a T&S display would have to intercept some RAM locations,
> as the electronics do not have any idea of the T&S. address 0x22 holds
> track, while 0x4d holds next sector to read (0x4c holds last sector
> read). I'm assuming one would just wire up a 573 to each address, and
> grab the data, converting it to decimal.
> 0x80 also states it is TRACK, with 0x81 being sector. These may be the
> bytes Drive Mirror was looking at, since they are so close together, it
> would be relatively easy to decode them.
Sure... wouldn't even take a '688 or other large address decoder. An
8-input NAND or two with an additional gate for 0x80 vs 0x81 for the
latch input. Hex to 2-digit BCD might be a bit hairy in TTL, though.
Did the Drive Mirror use PALs/GALs or straight TTL?
> I've got some Atmel AVR code here that could possibly be persuaded to
> "snoop" on the drive line and watch all the IEC commands, optionally
> outputting them to an LCD.
> I remember the ad for Drive Mirror, but I never have seen one.
Any idea how it mounted? Did you install flea clips? Solder on wires?
Plug into the CPU socket?
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Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
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