Created it, 06/10/19
Update it, 06/10/22
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4. - CONTROL OF THE OPERATION OF THE INTEGRATED CIRCUIT MM 74C04
Like first experiment, check the operation of an integrated circuit into 6 reversers, by recording the levels of tension high (or high state) and low (or low state) present at the entry and the exit of a reverser by means of the indicator with LED.
Let us see first of all which are the characteristics of this integrated circuit.
4. 1. - DESCRIPTION OF THE INTEGRATED CIRCUIT MM 74C04
With the first series of material that you bought or who you are in possession of an integrated circuit marked MM 74C04 or equivalent type, illustrated by the figure 13-a.
In the diagram of the figure 13-b, one can see that pin 1 corresponds to the entry of the first reverser, while its exit leads to pin 2. Pins 3, 5, 9, 11, 13 constitute the entries of the five other reversers whose exits correspond respectively to pins 4, 6, 8, 10, 12.
The six reversers are independent between them although they are contained in a single case by measurement of economy and with an aim of miniaturization.
On the other hand, their food is common: one must apply a positive tension ranging between + 3 and + 15 V to the marked pin 14 Vcc (for tension collector) or sometimes with symbol VD or VDD (for tension drain) ; one must, on the other hand, connect to the mass the marked pin 7 GND (for ground or ground in French) or sometimes VSS (for tension source).
This fork of supply voltage ranging between + 3 V and + 15 V is characteristic of the integrated circuits which you will use for the experiments and in general of most of the integrated circuits of family CMOS.
Other integrated circuits, pertaining to family TTL require, on the other hand, a supply voltage of + 5 V with a tolerance of ± 5 % ; for these circuits, a tension higher than 5,5 V would be undoubtedly destroying, while a value of tension lower than + 4,5 V could not guarantee a correct operation.
4. 2. - FIRST
EXPERIMENT : STUDY OF A NOT-CIRCUIT
With this experiment, you will study the operation of the first reverser contained in the integrated circuit whose entry is connected to pin 1 and the exit with pin 2
The five other reversers included in the same integrated circuit have an exactly identical operation of the first. You will be able to check them yourself one after the other if you wish it, by repeating the same operations.
The test consists in connecting the exit of the reverser in question to the indicator with LED, L0 is to be seen which levels of tension are obtained at exit according to levels' of tension present at the entry.
On the basis of these result, you will draw up the table of operation and the truth table of the reverser.
Now remove the integrated circuit MM 74C04
of graphited foam and introduce it into the support of test ICX,
by correctly directing it according to indications' of the figure 14-a and by
conforming you to the following instructions :
a) - Before introducing the integrated circuit into the support, examine its
pins carefully ; if one of them is twisted, rectify it using a brucelle
grip delicately.
b) - Present the integrated circuit on the support and check that the pins
correspond to the holes of the support ; if it is not the case, i.e. the
pins of the integrated circuit are slightly shifted (like illustrated appears
14-b), you must rectify them. For that, it is advisable to pose the circuit on
side on a hard level and to exert an adequate pressure so as to uniformly fold
the pins towards the interior, as indicated figure 15. The same operation must
be carried out on the other side of the integrated circuit, so that the two
lines of pins are folded symmetrically compared to the case.
c) - The pins of the integrated circuit being presented well opposite the holes
of the support (figure 14-c), press delicately but firmly on the integrated
circuit to plug in it in the support.
d) - By respecting the indications provided previously, prepare two pieces of
canned wire isolated from approximately 10 cm each one
in order to establish the connections between connectors.
e) - Using one of these wire, connect the exit of the
reverser, i.e. pin 2 at the entry
of the indicator with LED located by the L0 symbol
of the group of connectors.
f) - With the other wire, connect the entry of the
reverser, i.e. pin 1 with the
contact “-” group of connectors.
The connections carried out are represented on the figure 16-a and with them you carried out the circuit schematized by the figure 16-b.
As you can notice it, the connections relating to the supply voltage are not represented in this circuit, its value is not indicated there either: this is a convention generally adopted in the representation of the diagrams of the logical circuits. It remains however of course that the supply voltage owes, in each case, being present and to have a value appropriate to the fed circuits.
In the figure 16-b, the indicating circuit with LED is represented simply by a rectangle, because it does not form part of the logical circuit itself, but it is used only as an inspecting device. This rectangle thus represents the indicating circuit with LED, L0 with the corresponding transistor of order, whose complete diagram was already given figure 12.
You can see inside the graphic symbol of the reverser the indication 1 / 6 which means that the diagram represents one of the six reversers included in the same integrated circuit. However this fraction is often omitted by preoccupation with a simplification.
The number of the pin is deferred to the entry and the outlet side of the reverser. This indication is always on the diagrams of the logical circuits. It of a great utility for their comprehension in is seen of their practical realization.
g) - After having checked the exactitude of the connections carried out, feed
the circuit: i.e., connect the crocodile clips red and black to the pile while
respecting, of course, the polarities as you can do it now. You note that the LED
L0 ignites.
h) - Disconnect the pile. Remove the wire of the contact “-”
and introduce it into the contact “+”,
as represented on the figure 17-a. You carry out thus the circuit of the figure
17-b. Feed the circuit again. You note that the LED L0
dies out.
Figure 18 summarizes in the shape of a table the result obtained. The first column (entered) contains the levels of low tension (0 V) and high (4,5 V) applied to the entry of the reverser. In the second column (left) the states corresponding of the indicator to LED L0 connected on the outlet side of the same reverser appear.
You point out that the state of the indicator with LED means :
Lit LED = high level of tension
Extinct LED = level of low tension
Consider that a high level of tension is represented conventionally by the letter H (initial of the English word High, i.e. high) and a bottom grade of tension by the letter L (initial of the English word low meaning Low). One can transform the table of the figure 18-a into that of the figure 18-b called TABLE OF OPERATION of the reverser.
Into final, one can conclude on the basis from this table that the level of exit of a reverser is always the reverse of that of the entry, or that a bottom grade of entry corresponds to a high level of exit and vice versa.
The first finished experiment, disconnect the food of the circuit.
4. 3. - TRUTH TABLE OF THE REVERSER
You will see in the theory N° 3 that the circuits functioning with signals on two levels, high (positive tension) and low (null tension) as those of which we lay out, can provide two distinct switching functions according to whether one operates in positive or negative logic.
According to the positive logical convention which is used, on the bottom grade L is associated the logical state 0 and with the level H the logical state 1.
In this case, on the basis of the table of operation of the figure 18-b, one obtains the truth table of figure 19.
| Entry | Exit |
| 0 | 1 |
| 1 | 0 |
To define the characteristics of component of a numerical type, the manufacturers of integrated circuits generally provide the table of operation, sometimes the truth table or both.
To conclude, it should be noted that if one represents by the letter the input signal a, i.e. the variable from entry (1 or 0) and by the letter S the output signal from a reverser, relation flexible a and S can be written in the following form :
S = 
where the bar above letter a indicates the inversion of the logical output compared to that of the entry.
We will continue to deepen on the two other integrated circuits into knowing MM 74C08 and MM 74C00 about another page in order not to encumber this one.
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