16F877A won't keep relay on 100% of the time

[coyotegd]

Function Generator 12.1kHz TTL 3V signal directly on B0 and the relay works great. Ditto when the Generator's signal is run through PC parallel port input and tri-state transceiver to boost to 5V square wave.

Mach3 PC software transmitting 3V TTL through parallel printer port. Signal placed directly on B0, spastic relay. Ditto when the signal is passed through the tri-state transceiver.

Both signals look exactly the same on an oscilloscope. Both signals find the same ground as the PIC, relay, transceiver, parrallel port and power supply.

I even took the signal directly from the parallel port attached to the PC in case the cable was defective.

Arghhhhh.....

BTW, I believe "CMCON = 7" would be a moot entry. "ADCON1 = 7" makes ports A and E digital I/O rather than analog.