There are now three download sites, not just one. With hundreds of downloads per month, we were getting more traffic than my ISP could handle. Thanks to Peter Aigner for both the bug report and the correction. Both of them correct a bug in the earlier demo program that caused two LEDs to be on some of the time. You can probably build it using parts you already have on hand.
Capacitors are in microfarads.
It must be greater than 12.0 volts. The D0 output of from the PC controls this signal. No harm results from applying it at inopportune times. Pin B7 is both an input and an output. The PC reads the data on the BUSY pin, which is 0.6 volt higher than the output of the PIC because of D2.