How to Cascade Two Sets of 4-bit JK Flip-Flop Counters?

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Discussion Overview

The discussion revolves around the design and connection of two sets of 4-bit JK flip-flop counters to create an up-down counter that counts from 0 to 99. The participants explore methods for cascading the counters and triggering the second set based on the output of the first.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks guidance on how to connect two sets of 4-bit JK flip-flop counters to function as an up-down counter.
  • Another participant suggests using the falling pulse from the 4th JK counter to clock the second set of flip-flops, indicating the need to wire the first set as a BCD counter.
  • It is noted that the first set should provide outputs as powers of 2, with specific values assigned to each stage of the counter.
  • Alternative solutions are proposed, including using specific ICs like the 74LS192 or 4510 for counting up or down, which already provide BCD outputs.
  • A suggestion is made to use a 4518 or 40110 chip for counting, although these options are limited to counting up.
  • One participant mentions a K-mapping tutorial as a resource for designing counters, implying it could assist in the design process.

Areas of Agreement / Disagreement

Participants express various methods and ideas for cascading the counters, but there is no consensus on a single approach. Different opinions on the use of specific ICs and configurations remain present.

Contextual Notes

Some participants reference specific counting methods and ICs, but the discussion does not resolve the best approach for connecting the two sets of counters. Limitations in the designs and assumptions about the requirements for counting up and down are not fully explored.

Who May Find This Useful

Individuals interested in digital circuit design, particularly those working with flip-flops and counters, may find this discussion relevant.

KAS90
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hi there...
I wanted to ask about a way to cascade or let's say connect two sets of 4-bit flipflop JK counters together..
I want to create a circuit that is an up-down counter from 0 to 99..but as it is known, its difficult to use 8 inputs ofcourse.. so the best way is to have two sets of 4 jk flipflops..the first set will be connected to a 7seg and will count up and down, while the other one will not count up or down unless the first one has finished 10 counts..I hope u get what I mean..
the problem is that I didnt know how to connect the first circuit with the other one, in order for the first one to trigger the second one..do u guys have any idea how can I apply this? thanks a looot in advance :)
 
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The output of the 4th JK counter (X3 in the diagram below) falls when it clocks over from 9 to 0.
You can use this falling pulse to clock the next set of flip flops. You could invert it if the counter needed a rising edge.

You would wire the 1st 4 JKs as a BCD counter so that it divided by 10 but gave outputs from each stage as powers of 2.
So the 1st stage would give a 0 or a 1 and this would be worth 0 or 1.
But if the next stage gives a 1 it is worth 2. The next stage's 1 is worth 4 and the last one is worth 8.

So, 1 0 0 1 is worth 9.
Note the values from 10 to 15 cannot occur as this is a BCD counter.


deccount.gif


This would only count up as shown.


However, to do what you want, you could just get a 74LS192 chip or the 4510 which can count up or down, and already give BCD out.

If counting down wasn't important, you could get a 4518 which already has two BCD counters in the one chip, or the 40110 which already has 7 segment drivers in the counter chip. These only count up though.
 

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You can easily design any such counter using the K-mapping tutorial given in the instruction section of this site.

KM
 
Thanx guys that was a lot of help :) I really appreciate it..
but now I am having a problem connecting the two IC's.. I hope I figure it out..
 

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