Digital clock using discrete logic

techbud · 2019-09-12T01:34:57.0000000+03:00

The control logic is made using the 74HC157, which is a 8 lines to 4 lines multiplexer with 1 'select' pin. When the 'second' resets, the reset signal is also passed on to become the clock of the minute, same goes for the minute to the hour. But before those reset signal reach to clock pin of the next IC, they go through the multiplexer first. I added 2 buttons to act as 2 manual clock signals to control the 'minute' and the 'hour'. The multiplexer will select between the automated clock (the reset signals of the 'second' and 'minute') and the manual clock, HIGH for manual clock, LOW for automated clock. A double throw switch is connected to the 'select' pin of the MUX, which will also reset the second and stop it from counting. When the switch is set HIGH, the clock stop counting, 'second' goes to zero, and I can repeatedly press the two buttons to set the minute and the hour, then I set the switch LOW and the clock should go on counting like usual. The buttons have some bouncing issues, but by the time i realized it, it was too late to fix, it's kind of acceptable anyway, so not a big deal. reverse phone lookup nba reddit pcpartpicker