Byron!! Byron A Jeff wrote: It *DOES* make a difference where you put the resistor, since programmers invariably make *mistakes*. With only one resistor, it would be possible to burn out the left-hand port pin if you were to drive too many of the right-hand pins to the opposite polarity *simultaneously*. That's all. If you're careful, *really* careful, not to do that, then all is well with only one resistor. It makes absolutely no difference which side of the LED you put the resistor on, unless you want to use the roughly 1.3 V drop for some sort of measurement purposes. Use one "file" to hold bits to be driven during the "RED" cycle and another to hold bits to be driven during the "GREEN" cycle. Yellow gets a bit in both. Then cycle through both files, one bit at a time. That way you can be pretty certain you're not going to drive more than one LED at a time. How 'bout loading the flag file into the data output latches and then rotating the TRIS file with one bit cleared? :-) Now you know I'm going to have to build this thing, just to see it run. You might also wish to lower the value of the current- limiting resistor to allow the full 20mA that the pins can put through it. Since you're only going to be driving the LEDs for very small duty cycles (1/12 at most) you certainly won't have to worry about burning them out. -- Rick Miller