Posted by StevenRoy on November 07, 2000 at 20:41:07:
In Reply to: Cable problems. posted by Peter Cervenansky on November 07, 2000 at 10:15:02:
: Hi !
: I have a big problem. I need informations about C64 electronic circuit at JOYSTICK PORT 2.
: I have tried to connect my cable from PC paralell port to C64 joystick port 2 (4-bit data lines, 1 bit signal/button, 1 bit GND + my own software) a few days ago. Unfortunately, the result was - damaged C64 keyboard input/circuit.
: I need HELP! Is it correct to connect pins of PC to C64-pins ??? Is there 5V in C64 pins. ???
: Has anybody any infos ? Please send me more details ...
: Peter.
I tried something similar once, except that I connected the PC's printer port to the C64's user port. I managed to write a little program that transferred the entire contents of the C64's memory to the PC.
In theory, it should be possible to do something just like that with the joystick port, but I haven't tried it. The main thing to watch out for is that messing with the joystick ports will also affect the keyboard controller, possibly causing some difficulty with experimenting.
If you're trying to send data from the PC to the C64, you should (in theory) be able to just wire some of the data lines (output) from the PC printer port to the C64's joystick port (input).
To transfer any information back to the PC, though, you'd need to use some of the printer port's status lines for input (not the data lines). The nice thing is that you can just use the C64's DDR (Data Direction Register) to make any of the joystick port's pins into output lines. I love that feature.
This is all theoretical. Perhaps I should get out my old partially-functional C64 and experiment.
If I knew exactly what you needed this connection for, I may be able to be more helpful.