In the COMPUTER, and also in other devices of discrete equipment often there is a need for transformation of a n-digit binary code to a one-digit code with the basis of E=2n or the return transformation. The logic units which are carrying out such transformations are called respectively as decoders and shifrator. We will review examples of creation of shifrator and decoders on TE (threshold elements) and FN (formal neurons) below.
When using multiport PE with direct and inverse exits the decoder can be constructed on the same elements. In figure 3 the binary and octal decoder constructed on the same PE is shown, each of which has four entrances with scales +1 and one entrance weighing-1, a threshold +2, direct and inverse exits. Necessary functions of the decoder (1-this element are realized by connection of some entrances to constant logical levels 0 or 1 and removal of information from a direct or inverse exit of an element.
So, if, as a basic element of the decoder FN which is used in other devices as a reception element can apply. In this FN the OR entrance elements can be considered as elements I at negative logic. Removing information from an inverse exit of FN on similar elements, it is possible to realize function (1 decoders.
Similar situation takes place and in case of creation of decoders on PE and FN. For creation of the decoder on PE in the elementary case it is possible to take PE realizing function I and to construct the scheme completely identical to the scheme on valves. Thus both direct, and inverse values of arguments as the decoder realizes system of functions use
In figure 2 other option of the asynchronous binary and octal decoder in which only direct senses of arguments are used is shown. However a shortcoming as this, and the previous scheme it is possible to consider that in them polytypic elements are used.
Shifrator carries out function opposite to the decoder, that is will transform a one-digit code with E=2n basis to a n-digit binary code. At creation of a shifrator on PE and FN it is possible to use the elements realizing the OR function with straight lines and inverse exits. In figure 4 the example such vosmerichno a binary shifrator is shown.
In figure 1 the scheme of the three-input decoder on PE is shown. Characteristic of this decoder that it uses only direct senses of arguments and works by the synchronous principle. If on the tire C high potential is given, the decoder is open and works properly; if on this tire there is a low potential corresponding logical 0, the decoder is closed blocked) and at all its exits there are zero. It is obvious if to remove the tire of clock pulses and to lower thresholds of elements on unit, we will receive the asynchronous decoder with output dvukhvkhodovy elements.