- #1
smuscat
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I need some help how to build 8 bit up/down counter for my tracking ADC. All ideas are welcome.
How can i build 8 bit UP/DOWN counter using two 74191?
In summary, the individual is seeking assistance in building an 8-bit up/down counter for a tracking ADC, using two 74191 counters and a binary weighted resistors network. They have attempted to build the circuit but are encountering problems when counting down. They have received suggestions to check application notes for the 74191 and to get one counter working before adding the second one. The individual has also provided a description of how their circuit is supposed to work and the issue they are facing. They have also been directed to check what others have done for similar projects.
- #2
berkeman
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smuscat said:
Check out the first thread listed below in the "Similar Threads" section. Does it help?
- #3
smuscat
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berkeman said:
It didn't help me so much,his circuit is more complex than mine. I need how to connect the two 74191 to built an 8 bit up/down counter.My idea of the counter is to use it as DAC as binary weighted resistors network.Finally I want to built Tracking ADC.
- #4
berkeman
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smuscat said:
We don't do your school project work for you, smuscat. You need to do the bulk of the work. Show us your ideas about how to do the counter, and how you are going to use it as part of an ADC. Once you show us your work, we can offer tutorial comments that may help. You are required to do the bulk of the work on your project.
- #5
- #6
berkeman
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smuscat said:
Why are you using an opamp as a gate? Can you post your equations and K-Map that you used to design this? How did you derive that gate arrangement?
- #7
smuscat
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berkeman said:
The opamp is used as a compartor(+ i/p is from DAC, - i/p is analogue ) .When the second counter starts counting down ,the first counter is enabled to count down only when the second counter outputs are all 0.
- #8
skeptic2
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Why don't you get one counter working first and then add on the second one. Off hand it seems to me you have a number of errors. Have you looked for some application notes for the 74191? (AN 74191)
- #9
smuscat
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skeptic2 said:
I tried a single counter and it worked fine.The datasheet states that for cascading counters the ripple clock o/p of the 191 is fed to the clock i/p of the second 191 ,i tried it didn't worked when count down.My problem is when begins to count down.
- #10
skeptic2
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Which is your first 191 and which is your second?
- #11
smuscat
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skeptic2 said:
The first one is with the gates.
- #12
skeptic2
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I should have asked which is the lower 4 bit counter and which is the higher 4 bit counter?
It also might help if you could describe how it is supposed to work count by count. What is the state of the inputs and outputs when you start? What happens when your clock ripples from the first counter to the second one?
It also might help if you could describe how it is supposed to work count by count. What is the state of the inputs and outputs when you start? What happens when your clock ripples from the first counter to the second one?
- #13
smuscat
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skeptic2 said:
The lower bit counter is on top left corner of the image.The counter works as follows.
First, the Data inputs of the counters are all at 0 level.
When I load the inputs simultanously,the first counter starts to count up,when it reaches
maxium count the counter's ripple clock is fed to the second counter and continues to count, at this stage works perfectly!
The problem is when count down from the second counter to the first counter.
I tried to solve the problem by making a NOR gate from the outputs of the second counter
_
to the input of the UP/DOWN count first counter to enable the first counter ONLY to COUNT DOWN when the outputs of the second counters are all at 0 LEVEL.
- #14
skeptic2
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FAQ: How can i build 8 bit UP/DOWN counter using two 74191?
1. How do I connect the 74191 ICs to build an 8 bit UP/DOWN counter?
To build an 8 bit UP/DOWN counter using two 74191 ICs, you will need to connect the outputs of the first IC (Q0-Q3) to the inputs of the second IC (A1-A4). Additionally, you will need to connect the clock input (CP) of both ICs together, and connect the UP/DOWN (U/D) input of the second IC to a control signal which will determine the counting direction.
2. What is the function of the 74191 IC in the UP/DOWN counter?
The 74191 IC is a synchronous 4-bit binary UP/DOWN counter. This means that it can count up or down based on a control signal, and the outputs will change simultaneously at each clock pulse. In an 8 bit UP/DOWN counter, two 74191 ICs are cascaded together to create a larger counter with 8 bits.
3. How do I set the initial value for the counter?
To set the initial value for the counter, you will need to connect the desired binary number to the parallel data inputs (D0-D3) of the first IC. This will determine the starting value of the counter. It is important to note that this value should be within the range of 0-15 for a 4-bit counter, and 0-255 for an 8-bit counter.
4. Can I use a different IC instead of the 74191 for this UP/DOWN counter?
Yes, there are other ICs available that can be used to build an 8 bit UP/DOWN counter. Some examples include the 74LS191, 74HC191, or the 74HCT191. These ICs have similar functions and can be substituted in the circuit, but it is important to check the datasheet for any differences in pinouts or operating conditions.
5. How do I ensure that the counter counts in the correct direction?
The direction of the counter is determined by the UP/DOWN (U/D) input. If this input is connected to ground, the counter will count up, and if it is connected to a voltage source, the counter will count down. It is important to double check the connections and ensure that the control signal is set to the desired direction before powering on the circuit.