T-trigger. Principle of operation, functional diagrams

Trigger - the simplest device, which is a digital machine. It has two states of stability. One of these states is assigned the value "1", and the other "0". The state of the device, as well as the value of the binary information stored in it, is determined by the output signals: direct and inverse. In the case when a potential is established on the forward output, which corresponds to a logical unit, then the trigger state is called single (the potential on the inverse output corresponds to a logical zero). If there is no potential on the direct output, then the state of the trigger is called zero.

Classify the triggers in the following ways:

1. By the method of recorded information (asynchronous and synchronous).

2. By the method of information management (statistical, dynamic, single-stage, multi-stage).

3. By the way of realization of logical connections (JK-flip-flop, RS-flip-flops, T-flip-flop, D-flip-flop and other types).

The main parameters of all types of triggers are: the maximum duration of the input signal, the delay time necessary for switching the trigger, and also allowing the response time.

In this article, let's talk about this type of device, like - T-trigger. Such triggers have only one information (T) input, which is called a countable input. It changes its state after entering the counting (T) input of each control signal.

According to the table of transitions, the law of the functioning of such triggers is described by the characteristic equation: Q (t + 1) = TtQ't V T'tQt. From the equation it follows that when a logical zero arrives at the input (T), the T-trigger will retain its state, and change the opposite one when the logical one is applied.

It can be seen from the table that the T-flip-flop performs the addition operation, this caused the name of such a flip-flop to be countable, its information (T) input is a countable input. The signal level at the input of such a trigger appears twice as often as at its output (Q). Accordingly, the T-flip-flop is used as a frequency divider.

The T-trigger of an asynchronous type can be constructed on the basis of a two-stage RS flip-flop with additional connections, namely: the output of the flip-flop (Q) must be connected to the input (R), and the output (Q ') to the input (S). The information input (T) will be the synchronous input (C).

The photo shows a T-trigger. Functional scheme.

In the initial state, a logical zero level is fed to the information inputs of the trigger (R and S), when a logical zero is input to the counting (T) input, the state of the first trigger will be constantly copied by the second trigger, because the NAND item will output the logical unit level to Input of the second trigger. If the T-flip-flop is in the state of unity, then the inputs (R and S) will be fed with zero and unity levels, respectively. When the first signal arrives at the counting input of the logical unit, the logical unit is written into the first trigger. The state of the second trigger does not change, because the zero level from the output of the AND gate does not block its state. After the counting pulse is removed, the input (T) is set to zero, and the second trigger switches to the logical one state.

In the photo there is a synchronous T-trigger. Functional scheme.

Synchronous T-flip-flops are used, if necessary, to represent the potential of a logical unit sequence at the input of the T flip-flop.