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2003-05-02 18:06

Cybernator

Registered: Jun 2002
Posts: 154

Damn protocol

I've been trying to make the god damn 2bit ATN protocol work, but seems as if it doesn't like me. :P
It continues to lock up, and I have no idea what to do anymore. Never would have thought that it could be more problematic than the GCR reader.

Someone, please explain me how does the protocol work, step-by-step.

Otherwise, I'll have to break something in order to calm down. :P

Thanx for understanding. :)

ps. I have checked Krill's sources, as well as the sources of DreamLoad. It doesn't help.

2003-05-02 19:32

cadaver

Registered: Feb 2002
Posts: 1153

- In beginning all lines are high
- Diskdrive signals the C64 somehow of sector data ready, for example by pulling DATA low
- C64 notices this
- C64 requests first 2 databits by pulling ATN low

Repeat for each byte in sector:
- 1541 sends them (by tablelookup), with ATN A set
- C64 reads databits
- C64 requests next 2 databits by setting ATN high
- 1541 sends them, with ATN A not set
- C64 reads databits
- C64 requests next 2 databits by pulling ATN low
- 1541 sends them (by tablelookup), with ATN A set
- C64 reads databits
- C64 requests next 2 databits by setting ATN high
- 1541 sends them, with ATN A not set
- C64 reads databits, and sets ATN low for next byte

End of sector:
C64 releases ATN. 1541 sees this transition and sets CLK & DATA high again

2003-05-02 20:13

Cybernator

Registered: Jun 2002
Posts: 154

Thanks a lot! Although, it's a bit too late, as the TV set has two cracks on the top. :-) (Kidding as always ;))
Advice: never hit the TV set! It's the computer's fault... Or maybe the diskdrive's fault. :)

This info should help a lot. I'll see what I was doing wrong.
If it doesn't work this time, I may as well throw all my equipment, and start drinking. :)

Thanks again!

2004-08-19 21:24

St0fF

Registered: Oct 2002
Posts: 40

maybe you stumbled over the skipped input registers ... in DD00 the lines are low-active, in $1800 the lines are skipped to be kinda high-active which they in fact are not.
so the c64 must release the bits - setting them high! otherwise it won't be able to see any sent data - and lock up.
it just might be, that i switched something in my explanation - just recalled it after few years of no time 4 code ... but with the explanation in mind you'll be able to figure it out i hope ...

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