Operational tests of the
integrated circuit MM 74C00 NAND |
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Created it, 06/10/19
Update it, 06/10/22
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5. - OPERATIONAL TESTS OF THE INTEGRATED CIRCUIT MM 74C08
With the experiment which will follow, we will check in experiments the operation of an integrated circuit into four doors AND, type MM 74C08 or equivalent, and you will note in particular that a circuit AND can be used to allow or prohibit the passage of a binary digit depending on the state of an entry of order.
You will check by the practice the table of operation and the truth table of the circuit in question.
5. 1. - PRELIMINARY CONNECTIONS
a) - Remove all the connections made in the
preceding experiment.
b) - Remove the integrated circuit MM
74C04 of support ICX
; to carry out this operation, proceed in the following way :
delicately thread the blade of a screwdriver between
the case of the integrated circuit and the support.
turn the screwdriver : the integrated circuit
is raised as one sees it on the photograph of figure 20.
by making lever delicately with the screwdriver to
avoid deforming the pins of the integrated circuit, entirely remove this last
support.
c) - Introduce into support ICX
the integrated circuit MM 74C08
by respecting the precautions indicated during the assembly of the first
integrated circuit.
As one can see it in the diagram represented by the figure 21-c and provided by the manufacturer, the integrated circuit MM 74C08 contains 4 circuits AND having identical characteristics but functioning independently from/to each other. They have however a common food.
For this integrated circuit (as besides for all the integrated circuits in general) the classification of the pins corresponds to the sight of top ; pin 1 that which is near the mark bench (figure 21-a) or on the right a semicircular notch made on one on the small sides of the case, like is indicated on the figure 21-b.
5. 2. - SECOND EXPERIMENT : EXAMINATION OF A CIRCUIT AND
The experiment which follows relates to the first circuit AND whose two entries are pins 1 and 2 while the exit is pin 3.
Like it was already indicated, the three other circuits AND contents in the integrated circuit function in the same way. You will be able to thus check them easily by repeating the same tests.
The experiment consists in connecting the exit of the circuit AND with the indicator to LED, L0 in order to record the levels of output voltage corresponding to the various combinations of possible levels of tension on the entries.
Carry out the operations in the order by deferring you on the figure 22.
a) - Prepare a new piece of rigid wire isolated from
approximately 15 cm and connect the first entry, stitches 1,
of the circuit AND with the contact located
by - in top on the left of the whole
of the connectors. By this connection, the entry is put at the potential of the
mass.
b) - By means of the wire that you prepared (length
with your choice), connect the second entry of the circuit AND,
stitches 2, with the other contact located
by -, as represented on the figure
22-a ; this entry is thus ground connection.
c) - By means of an other piece of wire, connect the
exit, stitches 3, of the circuit AND
with the entry of the indicator with LED located by the L0
symbol on the group of connectors.
By these connections, you carried out the circuit represented figure 22-b (first test).
You can feed the circuit and observe the LED L0 : it remains extinct. You note thus that: when the entries of the circuit AND are both on the level of low tension, i.e. L, the exit is it also on the level L.
d) - Disconnect the food and now connect entry 2
to the contact located by the sign +,
as represented into dotted appears 22-a. In this manner, the second entry is not
any more on one level of low tension (0 V),
but on a High level of tension (+ 4,5 V).
The electric circuit relating to the new connections is also represented figure 22-b (second test).
Feed the circuit again and observe the LED L0 : it remains extinct. You thus note that: when an entry of the circuit AND is with the state H (high) and the other with the state L (low), the exit is maintained with the state L.
By convenience, the two tests of the experiment were represented on only one figure; to the first test entry 2 is connected to the mass and is on the level L, while with the second test, it is connected to the tension + 4,5 V and is then on the level H.
From these two experiments, you can deduce that, if one of the two entries (in our case the entry corresponding to pin 1) is on a bottom grade, the level which the other entry can take does not have any influence on the exit.
e) - Connect now entry 1
of the integrated circuit into the contact +
i.e. at the high level and by maintaining it in this position, repeat the two
preceding tests by connecting the entry 2d' access to the mass on the contact -,
as indicated figure 23-a (third test), and then on the contact +,
as indicated in dotted on the same figure (fourth test). The figure 23-b
represents the electric diagram of the circuit carried out.
The way of proceeding is always identical :
disconnect the food
carry out the connections
replug the food
observe the LED L0.
You note this time that entry 1 being on a high level, the exit takes the same level as that of the entry 2, i.e. it takes a bottom grade (L) if the level of entry 2 is low (L) or is levelled high (H) if the level of entry 2 is high (H).
This is operation characteristic of a circuit AND which can thus be used to order the transmission of a binary digit.
In this case, entry 1 is called entered of order, because if this entry is on the level L, the exit is insensitive with the variations of the level present on entry 2 ; while if entry 1 is on the level H, the exit takes the same level, high or low, that that present on entry 2.
Of course, the two entries being symmetrical, they are interchangeable, and entry 2 can become the entry of order if it is carried on the level H ; in this case, the exit will take the state corresponding to that of entry 1.
5. 3. - TABLE OF OPERATION AND TRUTH TABLE OF THE CIRCUIT AND (Return 3rd practice)
The tests carried out provide you all the useful data to draw up the table of operation of the circuit AND. You noted for example that with the two entries on the level L, the exit is on the level L.
You could then check for all the other combinations of levels of tension on the entries the levels of output voltage thanks to the observation of the LED L0.
Let us transcribe the results obtained in the TABLE OF OPERATION represented of figure 24.
By observing this table, you can conclude that in a circuit AND, the exit is on a high level (H) only when the entries are both on a high level (H) ; if one or the other or the two entries is on a bottom grade (L), the exit is on a bottom grade (L).
From the table of operation one can draw up the truth table by associating the level L the logical value 0 and the level H the logical value 1, as represented figure 25.
In this table, the two entries called a and b and the exit S is indicated by the numbers of the corresponding pins, because in the digital catalogs of circuits, the truth table is usually presented in this form.
This table describes the logical operation of the circuit AND. The exit S is in a logical state 1 only when the two entries a and b are both in a logical state 1.
This can also be expressed simply in the form :
S = a . b
or also, by neglecting the point, in the form :
S = ab
6. - OPERATIONAL
TESTS OF THE INTEGRATED
CIRCUIT MM 74C00 (Return
3rd practice)
The integrated circuit MM 74C00 contains 4 circuits NAND as represented figure 26. With the experiment which follows, you can note that a circuit NAND behaves like a circuit AND follow-up of a REVERSER.
6. 1. - THIRD EXPERIMENT : EXAMINATION OF A CIRCUIT NAND
a) - Disconnect the food and remove all the
connections carried out during the last experiment.
b) - Remove the integrated circuit MM
74C08 of the support of test ICX
and introduce into this last the new integrated circuit MM
74C00.
Now you can begin the operational test of first circuit NAND (its entries are pins 1 and 2 and the exit pin 3). You will proceed exactly in the same way as for the preceding experiment led on the circuit AND.
By carrying out the four possible combinations of states of the entries of circuit NAND, raise the state of the exit by observing each time the LED L0.
Using the results obtained, you can draw up the table of operation then the truth table of circuit NAND. These two tables are represented figure 27.
By comparing the table of operation of circuit NAND with that of the circuit AND, you can note that the levels of exit of circuit NAND can be obtained on the basis of those of the circuit AND by a simple inversion, i.e. while replacing in the last column relating to the exit, H by L and vice versa.
The same observation is valid for the truth table of the circuits AND and NAND where 0 logic is replaced by the 1 logic and vice versa.
This confirms that a circuit NAND is equivalent to a circuit AND follow-up of a reverser, as shown figure 28.
c) After having finished the experiment, remove the
integrated circuit MM 74C00 of the support
and replace it in graphited foam. With this practice, you finished the assembly
of the indicator with LED and its test.
By using the indicator with LED to visualize the levels of tension high and low at exit of a numerical integrated circuit, you analyzed the operation of some integrated circuits of which reversers, circuits AND and circuits NAND.
In the next practice, you will continue the wiring of the plate of the printed circuit and you will examine the operation of other types of circuits.
The various tests carried out with the transistors and diodes LED did not receive theoretical explanations yet, those are given in the new lessons of TECHNOLOGY 1 which treats semiconductors, (these lessons are very important for including/understanding the numerical system well, therefore not to neglect).
It will be interesting when you examine this technology to reconsider the practice N° 2 in order to better include/understand.
The sequence of the program can appear illogical to you but actually it is justified by the course of the practices and you will be able to see after having read five or six theories and five or six practical that those are complementary and allow, thanks to some returns behind, to carry out revisions in order to include/understand the important points well.
End of this 2nd practice.
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