Details

Entry by: Tim

Technology:  Pure 74XX TTL

Size: 5 TTL ICs, 7 LEDs, 4 Diodes, 5 Resistors

Description

This was not designed by me, but I found it in an ancient book from 1977 that I inherited . Of course we should rather report our own designs, but I will make an exception to set the bar low?!

This is a pure 7400 TTL implementation, taking five chips in total. You surely can beat that?

One curious fact is that it uses a ring oscillator based on NAND gates (lower left SN7400) as the clock. This will certainly ask for trouble when you start mixing logic IC with different propagation delays, but it appears this is fine when using only original TTL IC.