Date: 2006-06-06 13:10:59

Hallo allemaal,

I had another look at the predecessor of 1541LPT, PC-Flop, and I can announce some success! Having a fresh look at the whole again, I found out I made some mistakes in the past. So it seems I can continue this project as well.

What is interesting as well, I piggybacked some IC's on top of the 2nd 6522 that enable me to read a complete track. The next step is to replace the 6522 with this circuit as a stand alone one that should enable me to read the complete floppy through the LPT port. 
The circuit itself is quite simple: one 74HCT574, one 74LS74 and one 74LS04. The idea is simple as well: the 574 latches the data presented to Port A the moment 'Byte Ready' is active (L). As the 574 needs a rising edge, the 04 inverts this signal. The 74 latches the 'Byte Ready' signal as this one is only active for 1 uSec. One of the outputs of the LPT ports resets the 74 after reading the data. (Hmmmm, it seems I can simplify the circuit to just 2 IC's :)
And IMHO, by adding a 541, it should be even possible to use this circuit to write to disks. Unfortunately it requires about 7 outputs to control the various signals, more then available on one LPT port. But I already prooved that that isn't a problem when a COM port is present :)

It also looks as if my GCR encoding/decoding routines don't work right: if I encode 4 bytes and decode the result again, the resulting 4 bytes are not always the same as the beginning. Anyone willing to share his sources so I can see where I am going wrong? Many thanks in advance!

For anyone with more phantasy then me, I don't like the name PC-Flop. Anyone has an idea for a better name?

    / __|__
   / /  |_/     Groetjes, Ruud
   \ \__|_\
    \___|       URL: Ruud.C64.org



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