# 0-99 Counter

Discussion in 'Electronics Homework Help' started by tyhahn92, May 1, 2011.

1. ### tyhahn92

5
0
May 1, 2011
Hi everyone,

Long time reader but new to the forum, I was wandering if someone would be able to help me design this circuit for a class. No I don't want someone to just do my homework assignment for me, but our textbook is proving useless and there really is no help online that I can find.

The problem statement is....

design and build a counter circuit that counts from 00-99 using a well know IC
74163 counter and logic gates. Display the result using HEX displays.

I am using Logic Works 5 and I cannot get a the first Hex to get a number to start the counter and I cannot figure out how to make it stop at 99, or 63 hex. Any help would be amazing.

I've also included a picture of the circuit currently where I am stuck.

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119
27
Apr 21, 2011
You have missed a vital clue in the question.
The question is not clear, but it looks to me as though the counter should be a decimal counter, so the use of "HEX displays" might be misleading. Hex displays can show decimal or hex.

Can you clarify whether you are displaying a count to 99 in hex or decimal?

Last edited: May 1, 2011
3. ### tyhahn92

5
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May 1, 2011
I believe it should be count from 0-99 in decimal. Sorry for the confusion. We have only just started counters and most of the work we have done is with a simple D flip-flop's so I do not quite understand what I should have along with these 163's.

119
27
Apr 21, 2011
I have given you a hint. I do not want to tell you the answer.

I will give another clue though.

What does your counter normally count up to?
What do you want it to count to?

5. ### tyhahn92

5
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May 1, 2011
Okay, thank you for your help. I will try to add logic gates to the circuit so that it will reset when it gets to 99. Maybe you could also explain to me why the counter isn't counting in it's present state. Sorry I am new to this. When I click run the first display stays at 0 and the second displays stays at X so I know something isn't wired correctly but I do not know what.

119
27
Apr 21, 2011
I will need to read up on the datasheet to see what is wrong.

The first obvious error in the diagram is that CLR seems to be permanently asserted. Note the bubble at the input to CLR.

Maybe fix this while I read up.

119
27
Apr 21, 2011
I think you need a logic gate on each '163 to reset it when it gets to 9 (or maybe even binary equivalent of ten)

But I am giving the game away!

Had a look at the datasheet, and apart from the permanently asserted CLR problem, I see nothing wrong.

I am very rusty on logic circuits however, so I could easily have missed something.

Good luck....

8. ### tyhahn92

5
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May 1, 2011
Thank you very much.
I am not sure what is wrong with this circuit, you have helped an awful lot and the beginning part does count 0-9 but for some reason or another the second
one either isn't receiving the RCO count or some other issue because it just displays X the whole time. I've included another picture just in case you wanted to take another look, but thank you very much for your help.

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119
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Apr 21, 2011
You did well to get this far. I reckon you have earned a good homework mark already.

My reading of the datasheet suggest to me that your circuit shoud work. (which suggests that I do not understand it properly)

How about trying connection of the first CLR signal as the clock to the second counter. Don't know if this would work, but what have yo got to loose.

By the way..... you can cheat and use a 2 input NAND gate to detect Binary 9 or ten. The first time that outputs D and A (for 9) or D and B (for 10) both go high, is when the count is reached. No need to check the other 2 bits.

10. ### tyhahn92

5
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May 1, 2011
Good point on only checking the A and D inputs for a binary of value of nine.

I'm not sure what is wrong with the simulation because an X usually refers to a floating wire somewhere that is not connected all the way, but for some reason if I probe the QA, QB, QC, QD inputs, all of them say X even before the HEX display.

I attempted what you suggested with no luck and I also tried to use the CLR signal to be the RCO signal on the second part with also no luck, and have also rebuilt the circuit several times. There must be something small that I am missing.

I will continue to test around for a while, Thank you very much for your help.

11. ### Laplace

1,252
184
Apr 4, 2010
The internal RCO of the '163 only works for the binary mode. To run the '163 in decade mode you will have to use logic gates to generate the RCO the same way it is done for the '160 decade counter. Then use your generated RCO in the usual fashion. But also use the generated RCO to drive the synchronous CLR for the same stage (I'm assuming the CLR and LOAD inputs, with all DATA=0, work the same). So when the count reaches 9 there is a ripple carry and a reset to zero for each counter stage.

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Apr 21, 2011
@Laplace - nice catch. Makes sense now. Thanks

@tyhahn92 - presumably using the D output from the first stage as the clock input to the second stage would work. Not sure if an inverter would be needed.

13. ### conductor3

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Jun 7, 2011
also try a cd4026be ( 4000 series )is also a counter but goes to a common cathode 7 segment display directly............................................................................... post another tread if help is needed