The design operates by receiving a 10 MHz clock signal and using a frequency divider composed of a counter and a comparator to generate a 1 Hz output signal. This 1 Hz signal is used to feed an up-down counter circuit, which includes a synchronous enable to halt the count, a port to clear the count by setting the output to zero, and a port to indicate the desire to load a value directly from the circuit’s inputs. The value is loaded in the next clock cycle, and the count continues from that point. Finally, the count value is decoded into BCD code for display on a seven-segment display.
After resetting and setting the “en” port high, the device will begin a hexadecimal count with values ranging from 0 to F. Now, if the “up” port is set high, the count will be in ascending order, whereas if it’s set low, it will be in descending order. Additionally, there is an option to clear the count by raising the “syn_clear” port, which would reset the counter to zero. In the case where you want to load a value between 0 and F into the counter to start the count, you should set the “load” port high and then lower it to continue the count. The value to load will be taken directly from the first four input ports.
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | data in bit 0 | segment a | none |
| 1 | data in bit 1 | segment b | none |
| 2 | data in bit 2 | segment c | none |
| 3 | data in bit 3 | segment d | none |
| 4 | enable | segment e | none |
| 5 | syn_clear | segment f | none |
| 6 | up | segment g | none |
| 7 | load | dot | none |