Overview
A four digit decimal counter for the PIC 16F88 with the following features:
- Count up / down
- Reset
- Free running or hold on count over/underflow
- User count preset
- Over/underflow output
Schematic
Description
This is a 4 digit decimal counter which can operate as a free running counter or in count and hold mode with manual reset. In either mode the counter can be preset to count to a specified value. Clock edge and leading zero suppression can also be configured.
The 7-segment display and indicator LEDs are multiplexed. It will drive most common anode 7 segment LEDs. I used four single digit LEDs but a four digit LED module could also be used.
In free running mode the overflow output resets on the next clock pulse. Therefore the pulse duration is directly related to the input clock frequency.
The clock input goes to a Schmitt trigger input pin on the PIC. It will accept a 0-5V input signal only. If it's used with a mechanical switch you should use the debounce circuit shown on the schematic.
I've had the circuit clock reliably at 200Hz and it should be able to operate without missing a clock pulse at frequencies up to 5Khz.
Download circuit diagram