I'm playing around with some 7400 series logic, trying to teach myself the basics of digital design. I've been able to come up with a working circuit for a 24 hour digital clock easily, but I'm struggling trying to think of a way to make a 12 hour clock. Specifically my problem is the reset of the hours counter - when the tens digit of the hours section is 0 I need the units counter to count from 1 to 9 and roll over to 0 (for example 09 pm to 10 pm) but when the tens digit of the hours counter is a 1 I need the units counter to start counting at 1 (for example 12 pm - 1 am). I'm using 74LS93 series plain binary counters and assorted logic, and after working on it for a long while I can't think of a way to get it to work without using something like a presetable counter. Anyone have any ideas?
- posted
14 years ago