Ron Kneusel wrote:
Michael J. Mahon wrote:This is the $Csxx space, the slot entry point. It initializes the slot screen holes and the 6522 (for output on port A, and one input on port B). It also detects a CTL-I input, which signals a printer setup sequence.I'm not really interested in a printer driver but how difficult it would be to use this card to control other things, probably starting with simple LEDs on/off. I suppose it is time to dig out the old "6502 Software Design" book!
It would be quite easy. I, too, find the printer driver in ROM much less interesting than some other possibilities. ;-) All you need to do just about anything that can be done with two bidirectional handshaked parallel ports, a serial shift register serial I/O, and two timers--all with interrupt support--is a 6522 datasheet, which is readily available! -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."