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Forums > C64 Coding > How to receive a byte in 1541 drivecode?
2021-06-28 00:52
Zibri

Registered: May 2020
Posts: 159
How to receive a byte in 1541 drivecode?

Imagine this situation:

C64 SIDE:
open 15,8,15,"u3"
print#15,"ABCDE" : rem ANY LENGTH...
print#15,"X"
get#15,S$
close15

1541 side:
I don't understand how can I:
read a byte from IEC, wait for "X" and then send back a string.

Everything I tried failed.. I am missing something.
Can anyone help?
 
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2021-06-29 10:53
Krill

Registered: Apr 2002
Posts: 1973
Quoting Krill
you can deep-copy and modify the relevant bits at http://unusedino.de/ec64/technical/aay/c1541/ro41e85b.htm
Quoting Zibri
Clearly nobody knows the answer to my question.
Quoting Krill
you can deep-copy and modify the relevant bits at http://unusedino.de/ec64/technical/aay/c1541/ro41e85b.htm
Quoting Zibri
Yep.. exactly.. that's what I meant.
For now I don't have a good result.
Hence my question.
Pretty sure what i said IS an answer. Doing the actual gruntwork of reimplementing the protocol (and also make the code just snoop, not actually talk on the bus, which is a different beast) is left to the reader as an exercise.
2021-06-29 12:43
Martin Piper

Registered: Nov 2007
Posts: 432
I did a cartridge version of Summer Games that intercepted the kernal routines some returned the expected error. :)
2021-07-02 00:24
Zibri

Registered: May 2020
Posts: 159
Quote: I did a cartridge version of Summer Games that intercepted the kernal routines some returned the expected error. :)

Yep.. I do that often, but no, I was searching for a different thing. If nobody did it until now, the better... I will do it.
2021-07-02 00:26
Zibri

Registered: May 2020
Posts: 159
Quoting Krill
Doing the actual gruntwork of reimplementing the protocol (and also make the code just snoop, not actually talk on the bus, which is a different beast) is left to the reader as an exercise.

Yeah.. sure... that's why I asked. If I were able I would not have asked. But anyway.. ok... nobody clearly did it until now.
I'll see what I come up with.
2021-07-02 18:47
tlr

Registered: Sep 2003
Posts: 1460
If you are writing a passive analyzer it could be made to run on a second c64 connected to the same bus iec-bus.
2021-07-02 19:08
Groepaz

Registered: Dec 2001
Posts: 9969
I'd just clip the logic analyzer on the bus and then decode the capture, much easier :)
2021-07-04 16:13
Krill

Registered: Apr 2002
Posts: 1973
Quoting Groepaz
I'd just clip the logic analyzer on the bus and then decode the capture, much easier :)
Doing whatever with early 1980s stock hardware does have its charm, though. :)
2021-07-04 16:16
Krill

Registered: Apr 2002
Posts: 1973
Quoting tlr
If you are writing a passive analyzer it could be made to run on a second c64 connected to the same bus iec-bus.
Maybe, but the C-64's inability to read the state of the ATN line could be a problem.
2021-07-04 20:07
tlr

Registered: Sep 2003
Posts: 1460
Quote: Quoting tlr
If you are writing a passive analyzer it could be made to run on a second c64 connected to the same bus iec-bus.
Maybe, but the C-64's inability to read the state of the ATN line could be a problem.


Good point. Maybe a userport connection instead? A few resistors could be added to minimize the loading and perhaps also sampling $dd01 using a REU.
2021-07-04 20:29
Krill

Registered: Apr 2002
Posts: 1973
Quoting tlr
Good point. Maybe a userport connection instead? A few resistors could be added to minimize the loading and perhaps also sampling $dd01 using a REU.
Yes, either user port or joystick port(s). The latter could also sample real analogue values, perhaps, for a true stock hardware (except the adaptor) homebrew oscilloscope. Not sure how sensible that is, of course. =)
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