You should also re-evaluate the use of the HC109 flipflop in the configuration you have chosen. As it is now the flipflop can toggle at will whenever there is a clock on its input (unless the microcontroller is holding down on the clear ball). Once again, since it comes through a cable via the header, the 'HC109 clock should at least be buffered via a schmidt trigger type gate or buffer. Noise on this line could cause the HC109 to toggle inadvertantly and then cause the HC163 to clear before its time.

I do not understand the exact usage of this FF but maybe a more appropriate configuration would be a D type with the D tied high and then it clocks on only only once and the microcontroller takes care of starting the next cycle via the clear ball.


Michael Karas