Hello Matth,

M>>I want a PIC to generate a precision low output exactly once a second. The active low pulse needs to be about 120 microseconds long and must occur exactly once a second.<<

Assuming the low pulse is 5 volts.

TRISB=%00000000
Loop:
Portb.0=1
pauseUS 120
Portb.0=0
pauseUS 880
goto Loop

Get a accurate scope and measure it... if it needs to be adjusted, adjust the pause that you want.

Dwayne