INTRODUCTION
The main difference that elapses between the analogical
circuits and
those digitalizes them is in the fact who, in first, mark them are
characterize to you, to a data moment, from the value of the tension or
from that one of the current, while in the second ones they come only
indicates to you through two logical levels, that they can be indicates to
you with "true or false", "high or bottom", "1 or 0".
The two simple outlines, brought back in figures 1 and 2,
interpret, in the practical one, these last concepts.
Fig. 1 - With this simple outline the concept of logical
state "1", called also "true one" or "high" is defined. The switch set in 1 closes the local p0wer source on lamp LP, which is
ignited. The logical state goes characterized on the point To = 1.
Fig. 2 - The logical "0", called also "low" or "false"
state, is valued on the circuital point them To = 0. It is established from
the position of the switch KNOWS on 0, which maintains opened the circuit
of feeding of lamp LP that remains extinguished.
More just, in the outline of figure 1 logical level
"1" is come true, while in the outline of figure 2 logical level "0" is
caught up. In the first case state "1" corresponds to the circuit with
lamp LP ignited, in according to case logical state "0" corresponds to the
circuit with extinguished lamp LP.
In reference to the two outlines of
figures 1 and 2, we always remember that it is also used to say that, as a
result of the position assumed from switch (1 0 0), on the point To the
logical level can be "1" or "0".
The presence of lamp LP only serves to
confer a practical aspect to the two circuits, while that that imports
knowledge is which type of tension comes applied to LP, that positive +
VCC or that negative - VCC. To these in fact the two logical states
correspond.
Obviously, elaborating in more complex measure the two
logical states, they are constructed blots some electronic equipped of the
most complicated circuits and whose functions of elaboration exactly are
entrusted to those integrated members who take the name of and that, in
their constructive truth, are represent to you from elements of small
dimensions, in which they are concentrated migliaia of resistor, diode
valves and transistor.
The logical function necessarily is not
associated to largenesses electrical workers, but it remains defined from
those physics, the most varied. However, for clarity of language and
semplicità of interpretation, in the brought back examples always
reference is made to marks them electrical workers.
For the analysis of
the several logical functions they will come used of the said tables
TABLES VERITA' from which all can be deduced the possible
states, that is all the existing relations between income and escape
various pearls examined functions.