Synchronous BCD Up/Dn Counter - Help!

[richard_m]

Hi all,

Need some serious help with this. I'm trying to make a Synchronous BCD Up & Down Counter with also a carry/borrow function. I need to a decimal counter that on a button push will count up by one, and on a different button will count down by one. Also I need to be able to string several counters together to have more digits.

The closest thing I have is this:But I cannot see a way to convert it to a synchronous decimal counter.

I have been searching the web for solutions to this but no luck. Any help would be greatly appreciated.

Thanks in advance.

[Pauldf]

I'm not sure the diagram will work as such, your count down is connected to the inverted outputs and you basically have drawn a series of divide by two counters that will only count up (some other problems with the diagram but as it won't do what you want I won't go into them). The other problem with using any push button to create a pulse is what you call bounce, the switch wont make and break cleanly so you need to devise a circuit that cleans it up using op amps and capacitors or some sort of RS flip flop setup.

How about a kit from Velleman such as this: http://cpc.farnell.com/velleman-kit/k80 ... dp/HK00785

[richard_m]

Thanks paul,

That velleman kit may be exactly what I need.

Thanks

[piratepaul]

I need to look things up and think about it ... off the top of my head...

For up down use Q or NOT Q as they count in opposite directions.
To count up or down you pulse the clock.

You can get a single chip to do the counting, I am not sure what you want to borrow or carry adders and/or half adders.

I will look it up and get back to you.

Tar&stuff.

[piratepaul]

Sorry to count 1 you pulse the clock... for up or down change from Qto NOT Q.

Tar&stuff.