62. Implement T Latch
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Excitation Tables: An excitation table specifies the input conditions required to change a sequential circuit from the present state (Q_n) to the desired next state (Q_n+1).
JK Latch Excitation Table: The required J and K inputs for each state transition are given by the JK excitation table.
| Q_n | Q_n+1 | J | K |
|---|---|---|---|
| 0 | 0 | 0 | X |
| 0 | 1 | 1 | X |
| 1 | 0 | X | 1 |
| 1 | 1 | X | 0 |
Converting JK to T Latch: A T latch follows Q_n+1 = T ^ Q_n.
- T = 0: The latch must hold its state. Setting J = 0 and K = 0 satisfies both hold conditions.
- T = 1: The latch must toggle its state. Setting J = 1 and K = 1 satisfies both toggle conditions.
Hardware Implementation: Since J and K always have the same value as T, they are connected together to the T input. The latch therefore holds when T = 0 and toggles on each active enable when T = 1.