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Types of Latches and Flip Flops

    In this section we provide a summary of the operation tables and state transition tables for the common types of latches and flip flops. These tables will be useful for state machine design.

SR  

S R Qt+   $Q_t \to Q_{t+}$ S R
0 0 Qt hold $0 \to 0$ 0 $\phi$
0 1 0 reset $0 \to 1$ 1 0
1 0 1 set $1 \to 0$ 0 1
1 1 - invalid $1 \to 1$ $\phi$ 0

D  

D Qt+   $Q_t \to Q_{t+}$ D
0 0 reset $0 \to 0$ 0
1 1 set $0 \to 1$ 1
      $1 \to 0$ 0
      $1 \to 1$ 1

T  

T Qt+   $Q_t \to Q_{t+}$ T
0 Qt hold $0 \to 0$ 0
1 $\overline{Q}_t$ toggle $0 \to 1$ 1
      $1 \to 0$ 1
      $1 \to 1$ 0

JK  

J K Qt+   $Q_t \to Q_{t+}$ J K
0 0 Qt hold $0 \to 0$ 0 $\phi$
0 1 0 reset $0 \to 1$ 1 $\phi$
1 0 1 set $1 \to 0$ $\phi$ 1
1 1 $\overline{Q}_t$ toggle $1 \to 1$ $\phi$ 0


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