paravia@csd4.csd.uwm.edu (Mark David Kakatsch) (10/04/89)
A while ago, I remember seeing some postings on interfacing a 6522 w/ an Apple //e. Do any of you have experience with the Intel 8255? I've been reading a book called "Hardware Interfacing with the Apple II Plus", by John Uffenbeck, and it's got some simple schematics on ADC's and DAC's in it. The DAC uses an 8255 port, which is hooked up as follows: Data0-7 straight to D0-7 on the 8255(no buffer) R/W' is split into a RD' and WR' signal by a 'LS04 and applied to 5 and 36 on the 8255, respectively. A0 connected to A0(pin 9). A1 connected to A1(pin 8) DEV7' and A3 are NOR'd and fed to an inverter for the CS', so that it's only selected when DEV7' and A3' are both low. Port A is connected to the inputs on the MC1408 DAC. some assorted Analog stuff on the output side of the DAC. I looked at it w/ a 'scope and I see some pulses when I run a little loop which accesses the card's locations, but I get no change in the output voltage. When I outputted to the port, I could see no fluctuations on the Port A lines. Any help is really appreciated. Thanks. Mark -- | Albert Einstein got his name after he got| Mark D. Kakatsch | | smashed from drinking only one stein of | paravia@csd4.csd.uwm.edu | | beer. Hence; Albert EinStein. | ...uwmcsd1!uwmcsd4!paravia |