74192 not counting down from 5 - 0

[CraneWalker]

Hello, I am working on a digital game clock using down counters from 74192 and 7448 ICs.

I tried this following configuration and, when counting up, it counts from 0 to 5.

But when counting down, it is only stuck at 0. I've tried setting the counter from 5 before letting it count down, but again, it gets stuck at 0.

I am quite puzzled and frustrated about this issue. I swear I had it working as intended and even had a fully functioning circuit. After tinkering with the wire colors just so I can make the schematic much more readable for my groupmates and the professor, the counter just doesn't count down properly anymore.

I am using Proteus 8.1 SP1. Could it possibly be a technical glitch of some sort? Or maybe the connections are wrong? I've also tried using pull-up resistors but still, not working properly.



Regards, Crane

- - - Updated - - -

Apologies for the typo on the title. (Moderator action: corrected title)

 

[FvM]

The shown circuit will never count down.

The datasheet requires the inactive clock to be held at '1' rather than '0'.

 

[CraneWalker]

The shown circuit will never count down.

The datasheet requires the inactive clock to be held at '1' rather than '0'.

I reckon you mean I should leave the unused input at "1"?

I modified the circuit so that when I want it to count up, pin 4 is at logic "1", and vise versa.

It counts up as expected. However, it does not count down and is still stuck at zero.

 

[KlausST]

Hi,

I reckon you mean I should leave the unused input at "1"?

Why don´t you look into the datasheet on your own.
It leaves no doubt:


Klaus

 

[CraneWalker]

Yes, I understand that now and did just that in the previous post I made.

I am still working on the circuit and still, even when I set UP at logic '1', the circuit would still not count down properly and would get stuck at 0.

Could you please help me with this? I have been on this project for hours now, stumped and honestly getting really frustrated with it now.

Any help is very much appreciated.

 

[KlausST]

Hi,

and did just that in the previous post I made

Form your post#3 it is not clear how the inputs are driven.
--> show the complete circuit.

Consider to include some some debouncing circuit.

circuit would still not count down properly and would get stuck at 0.

According your circuit this is what you have designed.

--> See what is your "preset value"

Klaus

 

[CraneWalker]

I remade the circuit to make it more compact and hopefully easier to read.



I used a DPDT switch to control whether the circuit would count up or down while making sure the unused input be set at logic '1'.

It counts from 0 - 5 then loops back to 0 when it is counting up.

But while it does counts down normally, the circuit does not loop back to 5, which is most puzzling for me.

I also toyed with the circuit and found that the circuit will get stuck at 0 if I set it to skip 9. I find it hard to put it into words. The best I can describe it is that it refuses to not count 9 when it is counting down.

Kind regards, Crane

 

[CraneWalker]

I managed to make it count down from 5 to 0 and then looping back to 5.

I have forgotten about using PL, D0 and, D2 to make the counter skip to five after reaching zero.



Issue resolved.