In order to enhance the reliability of the trigger operation, it is essential that the output state changes only once per CLK cycle. This principle leads to the design of a pulse-triggered flip-flop based on the level-triggered flip-flop. The master-slave SR flip-flop, for instance, follows the characteristic equation: Q* = S + R'Q, with the constraint that SR = 0. This ensures that the flip-flop does not enter an undefined state when both S and R are active.
In a master-slave JK flip-flop, the behavior is divided into two distinct phases. When the clock signal (CP) is high (CP = 1), the master section receives the input signals and updates its internal state accordingly. During this time, the slave section remains in its previous state. However, when CP transitions from high to low (falling edge), the slave section captures the current state of the master and updates the output. As a result, the flip-flop only changes its output at the falling edge of the clock, which is referred to as master-slave triggering.
The characteristic equation for the JK flip-flop is given by: Q* = JQ' + K'Q. This equation describes how the next state (Q*) depends on the current state (Q) and the inputs J and K.
In pulse-triggered mode, the operation occurs in two steps. First, during the period when CLK = 1, the master flip-flop processes the input signals and sets itself to the appropriate state, while the slave remains unchanged. Then, at the falling edge of CLK, the slave flip-flop updates its state based on the master’s current state, causing the output terminals Q and Q’ to change.
It's important to note that the input signals must remain stable throughout the entire duration when CLK = 1. Any changes during this time could lead to unintended behavior or instability in the flip-flop.
One notable phenomenon in pulse-triggered flip-flops is the occurrence of "glitch" or "interference." For example, when Q = 0, a positive signal on the J input can cause an unexpected transition, and when Q = 1, a positive signal on the K input may have a similar effect. However, due to the design of the master-slave structure, the flip-flop ensures that the output changes only once per clock cycle, according to the input signals. This prevents multiple toggles and improves overall stability.
In practical use, the J and K inputs should be stable before the rising edge of the clock. Once the clock is high, these inputs should remain constant until the falling edge, at which point the flip-flop updates its state. This careful timing ensures reliable and predictable operation of the circuit.
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