Take a look at the circuit diagram. You recognize the synchronous counter and the logic gates that form the new input UP/DOWN...
Circuit diagram 2-bit UP/DOWN counter. |
Illustration states 2-bit UP/DOWN counter. |
When UP/DOWN = 0, the counter counts down...
When UP/DOWN = 1, the counter counts up...
Circuit 2-bit UP-DOWN counter. (Enlarge) |
The circuit looks complicated. However, it only ensures that either Q or Q' is passed to the next flip-flop.
In the next experiment you build a 4-bit UP/DOWN counter...
