Q. Graphic symbol of S-R flip-flop?

R-S Flip flop - Graphic symbol of S-R flip-flop is displayed in Fig below. It has 3 inputs S (set), R (reset) and C (for clock). Q(t+1) is next state of flip-flop after occurrence of a clock pulse.  Q(t) is present state which is present Q value (Set-1 or Reset- 0).

Figure: R-S Flip-flop

In figure (a) arrowhead symbol in front of clock pulse C denotes that flip-flop reacts to leading edge (from 0 to 1) of input clock signal. Operation of R-S flip-flop can be briefed as below:

1. If no clock signal it implies that C=0 then output can't change irrespective of R & S values.

2. When clock signal varies from 0 to 1 and S=1, R=0 then output Q=1 and Q¯ =0 (Set)

3. If R=1 S=0 and clock signal C alters from 0 to 1 then output Q=0 and Q¯ =1 (Reset)

4. At the time of positive clock transition if both S and R become 1 then output isn't defined as it might become 0 or 1 depending on internal timing delays taking place in circuit.