CMPSC 64 Lecture Notes - Lecture 15: Intime, Sequential Logic, Nor Gate
Document Summary
The output is a function only of the present inputs. The output is a function of both present and past inputs. Remember: in a nor gate, if at least 1 input is false, then the entire output is false. The result is that the output states (1 or 0) is maintained even if the input changes. Note that if one nor input is 0, the output becomes the inverse of the other input. As long as s=0 and r=0, the circuit output holds memory of its previous value (state) To change the output, just make s=1 and r=0 to make the output 1 (set), or s=0 and r=1 to make the output 0 (reset) Problem: this precludes a case when r = s = 0. You need this case if you want to preserve the previous output state. Adding an "enable" input: the gated sr latch. D input goes through only if an "enable input" (e) is 1.
