Flip-flops vs Latches a the names flip-flops and latches are sometimes used interchangeably: a flip-flops are clocked and latch are not a The term"flip-flop"is more appropriately associated with devices change state only on a clock edge or pulse, whereas latches change state without being clocked
•Flip-flops vs Latches ◼ The names flip-flops and latches are sometimes used interchangeably; ◼ Flip-flops are clocked and latch are not. ◼ The term “flip-flop” is more appropriately associated with devices change state only on a clock edge or pulse, whereas latches change state without being clocked
R-S NAND Latch ■ Analysis Q 口R=1,S=1Q=(SQ)y=Q Qn+=(RQ'=Q 口R=1,S=0Qm+=1 Q n+1 R 口R=0,5=1Qm1=0 Qm1=1 Q 口R=0,S=0Qm=1 Q+1=1
• R -S NAND Latch ◼ Analysis R=1, S=1 Qn+1=(SQ’)’=Q; Qn+1’=(RQ)’=Q’; R=1, S=0 Qn+1=1; Qn+1’=0; R=0, S=1 Qn+1=0; Qn+1’=1; R=0, S=0 Qn+1=1; Qn+1’=1; R S Q’ Q RS Q’ Q
Present state 0=0 =1 R=0,S=1 & & 0R01S1 Output next state 0=0 =1
& a & b Q' Q R S R=0, S=1 Q = 0 Q'= 1 1 1 0 0 1 0 1 0 Output next state Q = 0 Q'= 1 Present state
Present state 0=1 0=0 R=0.S=1 0 & & a O R Output next state 0=00=1
& a & b Q' Q R S R=0, S=1 Q = 1 Q'= 0 0 1 1 1 1 0 1 0 Output next state Q = 0 Q'= 1 Present state
Present state 0=00=1 R=1,S=0 0 Q & & 1 R 1 1S0 Output next state 0=1 0=0
R=1, S=0 Q = 0 Q'= 1 1 0 1 1 0 0 1 1 Output next state Q = 1 Q'= 0 & a & b Q' Q R S Present state