Nicron #38 13 июня 1997

Железо

Iron - work is an essential element of digital technology - a trigger.

           "Iron" ... logic!

(C) KLIM



  Hello, dear readers! Today, as promised,
We will analyze the work of a basic element of digital 
technology - Triggers.


  Sometimes the trigger is the trigger circuit or bistable
cell, since it has two stable states, each of
which can be as long as an external
signal will not be transferred to another stable sotoyanie.
Mechanical analog of the trigger switch is normal or
tumbler.

  The simplest trigger consists of two elements is not, entries 
and whose outputs are connected to the ring. With this inclusion

obtains a scheme with two stable states. Trigger
is an elementary memory cell, "remembers" the flow of
its input signal the unit. It can simulate
one digit binary number. Obviously, for the record
n-bit number to n flip-flops. For example, using
four triggers, you can record the numbers from 0 to 15.

  Consider the performance of two types of triggers: RS-trigger 
and T-trigger, with wide application.


  RS-flip-flop has two data inputs, which
received input signals. One input is denoted by the letter S on 
the English set, meaning "plant", and the other by the letter R

English reset-"dumping". Trigger denoted by the letters
Q and / Q. And the first of these is called the direct and the 
second - inverted. Symbol RS-flip-flop shown in Figure

1. If the input signal S enters 1, then the direct output
a signal of 1. This state is considered a trigger
unit.



  To translate the trigger in the zero state to file
a single signal to the input R, then the direct output will be 
zero signal and the output of the inversion will be a single 
signal. RS-triggers are used to store binary signals.


  T-flip-flop was named from the English word tumble
"Oprokidovatsya", or "flips" from the same word
is the name of the "tumbler". T-flip-flop is also called a 
countable trigger, because it is used for pulse counting.

T-flip-flop has a count input and two inverted and direct,
exit. Under the influence of signals coming to the counter 
input, trigger changes its state from zero to a single and

vice versa. Perebrasovany number corresponds exactly to the 
number of received signals. T-trigger is formed from the 
RS-flip-flop with Using a special control scheme. If you 
consistently join neskolko T-flip-flops, we get e

counter.

  Next we're going to disassemble the work of digital integrated
Chipset series K155.

[To be continued].