Master clock is fed through a prescaler with four tap-points which feeds a 4-bit ripple counter (there are 6 total bits, but the top two bits are discarded). 2:1 muxes are chained to act like a 8:1 mux for each LED segment position. As the counter runs, this results in each segment being turned on or off as needed to render the display sequence (NIC JAC ). The highest order bit is used to blink the decimal point on/off.
IN5 and IN6 selects the clock prescaler. OUT0-OUT7 are the LED segment outputs.
| # | Input | Output |
|---|---|---|
| 0 | clock | segment a |
| 1 | reset | segment b |
| 2 | none | segment c |
| 3 | none | segment d |
| 4 | none | segment e |
| 5 | Prescale select bit 0 | segment f |
| 6 | Prescale select bit 1 | segment g |
| 7 | none | segment dp |