# Triggers, Asynchronous RS-triggers on logical elements OR-HE and NAND - Informatics

## Triggers

The operation of the trigger is described by a table of states (switching, modes). The trigger state is determined by the signal Q on the forward output. For a complete description, all possible transitions from the two initial states must be reflected in the table: Q = 0 and Q = 1. Therefore, on the time diagrams that Micro-Logic II on the monitor screen, all possible state changes should also be reflected. Note that the dark rectangles on the timing diagrams obtained as a result of the simulation, mean the uncertainty of the values ​​of the values, ie. the value can take a value of both logical zero and one.

## Asynchronous RS-triggers on OR-HE and AND-NAN gateways

Trigger circuits with two generators D 0} and

02, which specify the sequence of change of input signals, are shown in Fig. 13.8, a, b. Temporal diagrams (Figure 13.8, c, d) allow us to identify the sequence of changes in the states (modes) of the trigger. The dark rectangles (9th clock) indicate the uncertainty of the values ​​of the output signals & lt; 2 and Q resulting from the transition from the prohibited mode (interval 8) to the storage mode (interval 9).

For the sake of clarity, all the data presented in the diagrams are given in Table. 13.1, which allows us to identify the features of transitions and states. For example, the trigger on the OR-NO elements in the state Q = 1 can go after giving two combinations of input signals SR = 10 and SR = 10, and with the combination SR = 00 can be in two states Q = 0 and Q = 1.

Table 13.1

 Inter Shafts S R Q States, Transitions 0 0 1 1 0 0 1 Initial state 1 1 0 0 1 1 0 Setting 1 of 0 (transition 0 → 1) 2 0 0 1 1 1 0 Storage 1 (transition 1 → 1) 3 1 0 0 1 1 0 Setting 1 of 1 (transition I → 1) 4 0 0 1 1 1 0 Storage (transition l → l) 5 0 1 1 0 0 1 Setting 0 of 1 (transition I → 0) 6 0 0 1 1 0 1 Storage 0 (transition 0 → 0) 7 0 1 1 0 0 1 Setting 0 from 0 (transition 0 → 0) 8 1 1 0 0 0 1 0 1 State not corresponding to trigger functions 9 0 0 1 1 ? ? Uncertain state

From Table. 13.1 (and time diagrams) it follows that the triggers on the elements OR-HE and N-HE can be called dual devices. Indeed, replacing the input signals R, S with inverse , R makes the operating modes of the triggers indistinguishable except for the forbidden mode. The difference between the states in the forbidden mode is highlighted in Table. 13.1 with a dark color.

Fig. 13.8. Schemes of asynchronous RS-triggers on the elements OR-HE (a), AND-N (b) and timing diagrams (in, d) their work

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