[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Help with Dual CF S-100 IDE VERSION 02

I've ran into an odd issue with IDE card.

The card has been fully built out.

Without the CF adapters installed the boards as expected. I'm able to write to all 6 TIL311's correctly; probing around the board everything looks as I would expect; the drive flip flop works etc.

When I plug in a CF adapter the ID0..ID4 signals are pulled to VSS (8255 Port A PA0..PA3 pins, CF adapters pins 11,13,15,17 ). It's definitely the CF adapter pulling the 4 pins low. I have 3 CF adapters, all three do this; both CF positions on the PCB result in the issue.

I've swapped put the 8255 and the 74LS244s (U12 and 14). At this point I'm lost.