Restrictions in input combinations of circuit?

Thread Starter

Gonzalo Armbrust

Joined Jun 28, 2015
16
I have a problem in which I am asked to " find any restrictions on the allowable input combinations on A and B"

I have designed a next state truth table for the problem in the attachements, however i'm confused as to what exactly is a restriction. I noticed that for when A = 0, B=0, it oscillates between 0 and 1, and 1 and 0 when the Q current state variable is changed and the P (output) is changed. There is a similar case for when A = 1, and B=1. If i'm understanding this correctly then, would the restrictions be that A cannot be equal to 1 and B cannot be equal to zero when Q is equal to 1...? And also A and B cannot be equal to 1 when Q is equal to 0..?
 

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GopherT

Joined Nov 23, 2012
7,983
I have a problem in which I am asked to " find any restrictions on the allowable input combinations on A and B"

I have designed a next state truth table for the problem in the attachements, however i'm confused as to what exactly is a restriction. I noticed that for when A = 0, B=0, it oscillates between 0 and 1, and 1 and 0 when the Q current state variable is changed and the P (output) is changed. There is a similar case for when A = 1, and B=1. If i'm understanding this correctly then, would the restrictions be that A cannot be equal to 1 and B cannot be equal to zero when Q is equal to 1...? And also A and B cannot be equal to 1 when Q is equal to 0..?
The lighting of the afternoon sun coming into your window has not been fully captured by your camera. I suggest something with higher resolution. I can't stand looking at anything with such low resolution when I think about the beauty that was missed in your attempt to capture this moment with a measly 4.9Mb file.

On the other hand, if you are just trying to ask for help, please use a low resolution image next time.
 

Thread Starter

Gonzalo Armbrust

Joined Jun 28, 2015
16
The lighting of the afternoon sun coming into your window has not been fully captured by your camera. I suggest something with higher resolution. I can't stand looking at anything with such low resolution when I think about the beauty that was missed in your attempt to capture this moment with a measly 4.9Mb file.

On the other hand, if you are just trying to ask for help, please use a low resolution image next time.
Here's the table I made, i'll just type it out:

present state / Next state
A | B | Q | Q | P (output)
0 0 0 0 1
0 0 1 0 1
0 1 0 0 1
0 1 1 1 0
1 0 0 0 1
1 0 1 0 1
1 1 0 0 1
1 1 1 1 0


Assuming that the table is correct, what would the restrictions be?
The circuit is just an S/R latch, with A and B fed into a NAND gate as the S input, and the value of B is the R input. I can post it if it's needed. P= Q'
 
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