(c) 64er magazin
Someone asked me about the parallel IEEE 488 interface for the VC1541, that has been published in an early issue of the famous german "64er" magazin. Well, I don't know if this magazin still exists (long out of the scene) but then I have this old issues in case I need to repair my interface.
I draw down the schematics long time ago and now I have scanned it
and
people who know what they are doing can see how to
produce such a board.
Hint: The ouput lines PA0-7, PB0-7 (Pins 2-17) and
CA1 and CA2 (Pins 40,39) arenot connected through to the motherboard!
vc1541.gif: The schematics in Compuserve (tm) GIF format.
Here you find the schematics in a text file together with some info how to build it.
In 1541par.mkrom.txt the basic file that patches the 1541 ROM is listed.
1541par.mkrom is the original C64 file.
All these files are in 1541par.tgz
(c) Commodore
I have drawn the schematics of the original Commodore C64 IEEE488 adaptor (in case I need to repair my own one...). Now I scanned them and put them here on the WEB. If you want to build yourself one, you have to add the ROM schematics. The interface used to have a ROM that maps itself to $8xxx at startup. The content is then copied to somewhere in $Cxxx, and the externel ROM is disabled. With the original software it was impossible to use both, the serial and the parallel interface at the same time (besides the fact that $Cxxx is occupied). So I wrote my own new kernel for the C64, where I replaced the cassette routines with the IEEE488 routines and a control byte determines which interface to use, separately for the devices from 4 to 10 (including).
The interface uses the standard 75160 and 75161 IEEE interface drivers and an unusual chip, the 6525 TPI (Tri Port Interface). Well, I doubt if one can get this chip today actually, but it has been used in the CBM 6x0 and 7x0 series computers.
The schematics in Compuserve (tm) GIF format. On my C64 kernel page the new kernel for the C64 can be found. The parallel IEEE488 routines are copied from the interface ROM, I think I should mention that.
Long time ago, when I had an Atari ST, I built a ROM-Port interface
for an IEEE488 bus. For this I wrote an Accessory, so that the Atari
could serve the IEEE488 requests in the background.
Especially I would like to warn you about fiddling around with a soldering
iron on the Atari ST board. It is such a poor quality that only people
with lots of experience should think of doing it.
(I'm not one of them...) My Atari ST died because some signal lines broke
and I had to fix them and so on...
This interface is covered by the
GNU public license.
The schematics in Compuserve (tm) GIF format. The english doc is in the file iec-engl.doc, while the archive iecst.lzh has all, the schematicve, the docs, the source and a binary.
