I have problem with understanding the feedback part in flip flop. Consider a flip-flop circuit containing just two NAND gates as shown in the picture below:
Problem 1) Let A & S' be the inputs of 1st NAND gate and B & R' be the inputs of the 2nd NAND gate. What will be the values of A & B when both S' & R' are 0? (To find output we need to know the inputs, but here the inputs are depended upon the outputs of each other which makes me confused!)
Problem 2) If A & S' are 0, Q will become 1. Since Q=B, B will also become 1. Now let R'=0, then Q' will become 1. Since Q'=A, A will change to 1 from 0. Is this analysis true?
Best Answer
Problem 1)
Basically start by saying S' is 0, this means that Q will be 1 (as the NAND gate is high when Either A or S' is low), therefore B will be 1. As B is one the inputs to the second gate are 1 and 0 therefore Q' is 1. So A will be 1. The inputs to the first gate will be 1 and 0 so Q will still be 1.
Problem 2)
A will change from a 0 to a 1 but Q will still be high as S' is still 0