State transition diagram and stimulus table of trigger

Description The logical function of the trigger can also be described graphically, i.e., in a state transition diagram. Figure 13-4 is a state transition diagram of a basic trigger. The two circles in the figure represent the two stable states of the basic trigger, the arrow indicates the direction of state transition under the action of the input signal, and the annotation next to the arrow indicates the condition of state transition.

As shown in Figure 13-4, if the current stable state of the trigger is Qn=0, then under the condition of the input signal , the trigger transfers to the next state (next state) Qn+1=1; if the input signal or 1, the trigger remains at 0; if the current stable state of the trigger is Qn=1, then under the action of the input signal , the trigger transfers to the next state (next state) Qn+1=0; if the input signal , the trigger remains at 1. This is consistent with the function described in Table 13-1.
Table 13-3 can be easily listed from Figure 13-4. Table 13-3 shows the requirements for the input signal when the trigger transfers from the current state Qn to the next state Qn+1 of the specified requirement. Therefore, Table 13-3 is the excitation table or drive table of the trigger. It is essentially a derivative table of the state transition truth table in Table 13-1. The
above several description methods of the logic function of the trigger are essentially the same and can be converted to each other. When analyzing the logic circuit containing the trigger, it is necessary to skillfully use the state transition truth table, state equation and state transition diagram. When designing a logic circuit (sequential logic circuit) that includes a trigger, the trigger excitation table must be used.