# Need Help with My BCD Counter Design

#### Yaaw

Joined Oct 17, 2023
4
So I based on the Title I need help with my counter, I want to stop the counter from counting after it reaches 0 on the 7 segment display, So even if I pushed the CLK (pin15) when at 0, it wont go back to 9. This is my Circuit Design so far.

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#### Ian0

Joined Aug 7, 2020
9,499
I'll give you a clue:
use CLOCK INHIBIT input

#### MrChips

Joined Oct 2, 2009
30,476
Also, you will definitely need to debounce the CLOCK push-button.

#### Yaaw

Joined Oct 17, 2023
4
Also, you will definitely need to debounce the CLOCK push-button.

#### Yaaw

Joined Oct 17, 2023
4
I'll give you a clue:
use CLOCK INHIBIT input
I know that cutting the connection of Clock Inhibit to GND would stop the count, but In my knowledge it has to be a form of a switch. I just want to automatically cut the connection, just like a countdown timer. Are there any other way to this?.

#### MrChips

Joined Oct 2, 2009
30,476
Search for switch debouncing techniques.

#### MrChips

Joined Oct 2, 2009
30,476
I know that cutting the connection of Clock Inhibit to GND would stop the count, but In my knowledge it has to be a form of a switch. I just want to automatically cut the connection, just like a countdown timer. Are there any other way to this?.
Logic gates are called "gates" for a reason.

Study how a 2-INPUT AND gate works.
Then study De Morgan's equivalent gates.

#### Yaaw

Joined Oct 17, 2023
4
Logic gates are called "gates" for a reason.

Study how a 2-INPUT AND gate works.
Then study De Morgan's equivalent gates.
Ohhh, I see, I just have to input the CI with High Input, and this comes from inverting the binary 0000 = 0 (now 1) and then adding them up using and gates.

#### dl324

Joined Mar 30, 2015
16,679
I want to stop the counter from counting after it reaches 0 on the 7 segment display
You have a switch that allows you to switch between up and down counting. It would be helpful if you stated which direction it's counting.
EDIT: corrected grammar - missing apostrophe.
You don't have to worry about switch bounce in a simulator.
I know that cutting the connection of Clock Inhibit to GND would stop the count, but In my knowledge it has to be a form of a switch.
What makes you say that? It would be more typical to use gates/flip flops to implement your stop feature.

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#### MrChips

Joined Oct 2, 2009
30,476
You don't have to worry about switch bounce in a simulator.
This is another example of how simulators can lead you astray.

#### crutschow

Joined Mar 14, 2008
34,047
This is another example of how simulators can lead you astray.
So can a circuit breadboard, if you don't take the real characteristics/tolerances of the devices into account, when you translate it into a PCB circuit.

A simulator is like any other tool (and it's a very good tool).
If you don't know its limitations, you will likely get bit in the posterior.
The limitations don't mean it's a bad tool.

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#### Audioguru again

Joined Oct 21, 2019
6,610
Mixing logic types does not work.
A CD4510 is Cmos and has a very low output-low current.
An SN7404 is very old TTL and has a very high input-low current.

#### dl324

Joined Mar 30, 2015
16,679
I need help with my counter, I want to stop the counter from counting after it reaches 0 on the 7 segment display, So even if I pushed the CLK (pin15) when at 0, it wont go back to 9. This is my Circuit Design so far.
When is your assignment due? Are there any constraints on how you're supposed to implement the stop feature?