M200 interfacing continues...

Ok, I'm almost there. I've got everything wired up and most of the driver software done. The main problem I'm having is reading the control lines of the 6522. According to the spec sheet, CB1, CB2 and CA2 are all supposed to be TTL level outputs when programmed for such. So they are, but I'm having trouble reading CB2 reliably. I put a pull-down resistor on it but that doesn't help. The signal to it is spotty for some reason. I've got the PICK CHECK signal from the reader going into CB2. I have a 1K resistor going from CB2 to ground. READER SIGNAL----+----/\/\/\-------GND | | 6522 CB2 If there's an error (misfeed for instance) CB2 should get a logical TRUE. This works sometimes, but not always. And it's the same whether I have the pull-down resistor or not. I'm using CB1 reliable without the need of a pull-down resistor. I don't know if it's sloppy code or a bug, but the Apple doesn't seem fast enough to read and process the data character by character. I would think that it should be fast enough to do so but I'll have to check the timing on the loop and see if it falls within the specs of each column read from the reader. For now I've switched to buffering the data and then processing it after each card read, controlling the picker with the software to control the flow of cards. I'm figuring out the code for the last piece which decodes the row pin into a decimal number. What's the best way to do an nth root operation in 6502 assembly? :) Crummy way: LDY #00 LOOP INY LSR BCC LOOP This assumes only 1 bit is set in the accumulator. It loops until the bit falls off from the LSR operation. Assuming the accumulator has #80 to begin with, the Y-register result should be 8. -- Sellam Ismail Vintage Computer Festival ------------------------------------------------------------------------------ International Man of Intrigue and Danger http://www.vintage.org * Old computing resources for business and academia at www.VintageTech.com *