On Wed, Nov 18, 2015 at 2:48 AM, Eric Smith <space...@gmail.com> wrote: > I've designed a simple adapter PCB [for the DC37S floppy connector of the Western Digital WD900/WD9000 Pascal Microengine] > To support proper head load or motor spinup timing, I put an optional > PIC microcontroller and DIP switch on the adapter, to act as a digital > delay between HLD and HLT, with sixteen switch-selectable delays.
I've got the PIC code written and tested (standalone). I saw some really weird behavior at first. There's a 10K SIP resistor network for pullups, and I'd installed it backwards, so there was 20K between logic signals instead of 10K between each and the +5V low-impedance power rail. Since some of those logic signals were intended to be driven by open-collector drivers, and weren't being drive, it looked like the PIC was mysteriously driving some pins configured as inputs. Once I figured that out and fixed it, the code worked fine.
