# Numbers jump when carry is low on a BCD counter

#### Orbitingful

Joined Oct 31, 2015
32
I am using two 4510 counters which I want to connect together so I can count from 0-99. I have connected carry of the right BCD to the clock of the left. However when carry is low, and I change the direction of the BCD, the left number jumps. Carry is low when the number is 0 when counting down and 9 when counting up. So if I have a number containing 0, e.g. 60, and I change the direction to count down, the number jumps. How can I stop the numbers jumping when changing the direction at 0 carry?

Thanks for the help. I can include a schematic.

#### AnalogKid

Joined Aug 1, 2013
11,196
This is a circuit design forum. No schematic = very iffy answers.

ak

#### dl324

Joined Mar 30, 2015
17,110
I have connected carry of the right BCD to the clock of the left. However when carry is low, and I change the direction of the BCD, the left number jumps. Carry is low when the number is 0 when counting down and 9 when counting up. So if I have a number containing 0, e.g. 60, and I change the direction to count down, the number jumps. How can I stop the numbers jumping when changing the direction at 0 carry?
Post a schematic and be more precise with your description. The counter has pins for carry out and carry in. Which are you referring to when you say carry?

Do both digits "jump"? Does jump mean change by one digit (e.g. 0 to 1 or 0 to 9), or do they jump by several numbers?

#### hp1729

Joined Nov 23, 2015
2,304
I am using two 4510 counters which I want to connect together so I can count from 0-99. I have connected carry of the right BCD to the clock of the left. However when carry is low, and I change the direction of the BCD, the left number jumps. Carry is low when the number is 0 when counting down and 9 when counting up. So if I have a number containing 0, e.g. 60, and I change the direction to count down, the number jumps. How can I stop the numbers jumping when changing the direction at 0 carry?

Thanks for the help. I can include a schematic.
How close is this to what you have?
It counts up and down with no unexpected behavior.

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