Frequency Counter

Now that we have a working counter and display the next thing to look at is the timebase. The timebase I built when first working on this counter is odd. It uses, for some reason, a 3.2768MHz crystal divided by (2^16 * 10n) to get a gate pulse which is a multiple of 1s, then further divided and decoded by a 3-to-8 decoder to generate pulses which latch the counter onto the display, and reset the counters. This much was copied from EMRFD but without the intelligence that excellent book expects: obviously, this solution is fine for a quick gate but highly tedious for the long gates I decided to add, as well as being useless for pulse-width-counting, which I wanted to make it do like G0UPL’s counter—the other project I copied rather blindly. I’d be much better off with a 10 or 20MHz crystal and drop the needless 2^16 counter. But more on that later when I finish it.

I started this peice of test equipment when I was about 15, I think, built the timebase with enthusiasm, the counting chain with a bit less, and then wondered how on earth I was to attach the 7-segment displays. Surely not one wire each?! So the project languished, and eventually got relegated to the shelf without ever being finished. All I had was the breadboard and two schematics which nearly corresponded with what was in front of me: