Study
of a Synchronous Meter/Discounting machine (UP/DOWN) on four floors MM
74C193 |
Electronic
play carried out with a Meter |
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Created it, 06/10/19
Update it, 06/10/29
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8. - SEVENTH EXPERIMENT : USE OF THE CIRCUIT MM 74C163 LIKE PROGRAMMABLE DIVIDER
In the preceding experiment, the exit CARRY was permanently on the level L, therefore it was not possible to exploit it.
Nevertheless, if one wishes to mount several meters in cascade, it is necessary to connect the exit CARRY of a meter to the following meter. Indeed, as soon as a meter reaches its maximum capacity, the exit CARRY passes in a high state and allows the validation of the following meter. This last will take into account the clock signal which will follow.
In this experiment, you will produce a meter with variable, programmable module and using the exit CARRY. In addition, entry LOAD is used to allow the programming.
8. 1. - REALIZATION OF THE CIRCUIT
a) Remove all the connections relating to the preceding experiment. Leave in place the integrated circuits MM 74C163 and MM 74C00.
b) Carry out the connections indicated to the figure 21-a. The electric diagram of the assembly carried out is given to the figure 21-b. The signal present on the exit CARRY is the reverse of that present on entry LOAD.
8. 2. - OPERATIONAL TESTS
a) Put the switches on position 0 then put the digilab under tension.
b) Maintain P1 supported and to actuate P0. The four LED are extinct. The meter is given to zero.
c) Slacken P1 and put switch SW0 on position 0, SW1 out of 1, SW2 out of 0 and SW3 out of 1.
The meter is thus prépositionné to 10.
d) Support on fifteen recoveries on P0. The meter passes successively from state 0 to state 15.
In state 15, the exit CARRY passes on the level H and entry LOAD passes on the level L.
e) Support again on P0.
The LED L1 and L3 are lit and the LED L0 and L2 are extinct.
The meter is thus positioned with state 10. Indeed, entry LOAD was on the level L and the meter was prépositionné in the state or were four entries IN1, IN2, IN3 and IN4.
f) Support on several occasions on P0. You notice that the meter does not take any the states ranging between 0 and 9 but only those ranging between 10 and 15. It is indeed a meter modulo 6.
This appears on the figure 22.
g) Move the connection of
entry CLOCK of the contact P0
to contact CP1.
In addition, lay out the generator of clock of the digilab on frequency 1 Hz.
This assembly functions like a divider by 6. You observe well that the LED L7 ignites periodically every six seconds.
h) Repeat the experiment by changing the logical combination of four entries IN1, IN2, IN3 and IN4.
You observe that the frequency of lighting of the LED L7 is related directly to this combination.
In conclusion, this experiment shows you how to use the circuit MM 74C163 like divider and programmable meter.
To obtain the module of the produced meter, it is enough to withdraw maximum number of states to the integrated circuit the number posted on entries IN1, IN2, IN3 and IN4.
In this experiment, the module was worth 6 (16 - 10 = 6).
This meter is programmable since it is enough to put the combination desired on four entries IN1, IN2, IN3 and IN4.
On the other hand, compared to the preceding experiment, this meter modulo 6 does not pass by state 0.
Practically, it is the type of application which makes it possible to choose one or the other of the two assemblies proposed.
9. - EIGHTH EXPERIMENT : STUDY OF A SYNCHRONOUS METER
/ DISCOUNTING MACHINE (UP / DOWN) A FOUR STAGES
The various meters examined until now have a mode of increasing counting.
On the level of the diagram of the states, the progression of a state to the following is always carried out in the same direction.
There are also discounting machines, whose progression is carried out in the opposite direction.
The same integrated circuit can function in counting mode or in countdown mode.
An example of application is the determination of the number of people in a part.
For that, it is enough to use two photocells detecting the direction of crossing of the door.
When a person enters, the meter is incremented of a unit, i.e. it immediately passes to the higher number.
When a person leaves, the meter is décrémenté of a unit.
The meter passes to the immediately lower number. Therefore, it is possible to know the exact number constantly people being in the part.
With this new experiment, you will check the operation of a new integrated circuit, the MM 74C193.
It is a synchronous reversible counter on four floors. This one is rather similar to the MM 74C163.
It has, indeed, an entry LOAD and four entries IN1, IN2, IN3 and IN4 allowing presetting.
Figure 23 illustrates the logic diagram of this circuit and figure 24 its stitching.
As you see it on figure 23, this meter consists of four rockers of the type D assembled out of divider by 2 (the entry T = Toggle is the entry of clock), i.e. they change logical state to each clock pulse arriving on the entry T.
It is about the assembly proposed in the first experiment where a rocker of the type D is assembled out of divider by 2.
The four exits are always indicated Q1, Q2, Q3 and Q4.
Entry CLEAR makes it possible to force the meter with zero. It is active on the level H.
Entry LOAD is active on the level L. These two entries are asynchronous, therefore active independently of the clock.
This circuit has, moreover, two entries called COUNT UP and COUNT DOWN.
It is they which make it possible to use the integrated circuit in counting mode or in countdown mode.
In counting mode, the clock is applied to entry COUNT UP and entry COUNT DOWN is cabled at the logical level H.
When the meter is to 15 and entry COUNT UP on the level L, the exit CARRY passes on the level L.
In countdown mode, it is the entry COUNT DOWN which receives the clock signal, whereas entry COUNT UP is cabled at the logical level H.
When the meter is to 0 and entry COUNT DOWN on the level L, exit BORROW (retained) passes on the level L.
This exit is used when several meters are assembled in cascade.
9. 1. - REALIZATION OF THE CIRCUIT
a) Remove the connections relating to the preceding experiment as well as the integrated circuits assembled on the matrix.
b) Insert the integrated circuit MM 74C193 on the matrix and carry out the connections indicated to the figure 25-a.
The electric diagram of the circuit carried out is given to the figure 25-b.
9. 2. - OPERATIONAL TEST
a) Put SW0 on position 0 and SW1 on position 1.
b) Put the digilab under tension.
The LED L6 and L7 are lit.
c) Put SW0 on position 1.
The LED L0, L1, L2 and L3 are extinct. The LED L7 and L6 remain lit. The meter is to 0.
d) Put SW0 on position 0.
Entry CLEAR is thus inactive. Temporarily put SW1 on position 0 then reconsider position 1. Thus, you activate entry LOAD. The LED L0, L2 and L3 are lit, while L1 remains extinct.
Entries IN1, IN2, IN3 and IN4 are in logical states corresponding to state 13.
IN1 is in a high state (1)
IN2 is in a low state (0)
IN3 is in a high state (1)
IN4 is in a high state (1).
As long as you do not press on the buttons P0 and P1, entries COUNT UP and COUNT DOWN are on the level H.
It will thus be enough to support on P1 or P0 according to the mode (counting or countdown) desired.
The active face will take place when you slacken the selected button.
e) Support on P1 then slacken this button. The meter passed to the state 14.
f) Support again on P1 and slacken it. The meter passes to state 15 ; the four LED L0, L1, L2 and L3 ignite.
g) Support on P1 and maintain it in this position. The LED L6 which corresponds to the exit CURRY extinguishes. This confirms that the meter reached its maximum capacity.
h) Slacken the P1 button. The meter passes to state 0. The LED L0, L1, L2 and L3 are extinct. The LED L6 is re-ignited.
i) Support again twice on P1. The meter passes to state 2 (L0 extinct, L1 lit, L2 extinct, L3 extinct).
j) Support once on P0 and slacken it. The meter passes to state 1. Support once again on P0 and slacken it. The meter passes to state 0.
k) Support on P0 and thus maintain it. The LED L7 dies out. This confirms that the meter reached state 0.
l) Slacken P0. The meter passes to state 15 and the LED L7 is re-ignited. If you continue to support on P0, the meter is décrémenté of a unit to each impulse.
You can alternatively support on several occasions on P0 or P1.
In a case, you décrémentez the meter, in the other case, you increment it.
To conclude, it is possible to give the essential characteristics of this circuit MM 74C193 :
entry CLEAR is
active on the level H and takes precedence
over all the other entries.
when one applies a level L
to entry LOAD, the meter passes to the state
corresponding to entries IN1, IN2, IN3 and IN4
if entry CLEAR is on the level L.
entries CLEAR
and LOAD are asynchronous.
a transition from L
to H on entry COUNT
UP determines an incrementing of the meter.
a transition from L
to H on entry COUNT
DOWN determines a decrementation of the meter.
the exit CARRY
passes on the level L at the time when entry
COUNT UP returns on the level L
and which the meter is with state 15.
With the following transition from L to H of entry COUNT UP, the exit CARRY passes by again on the level H, thus generating an impulse of carryforward for the possible following meter.
exit BORROW
passes on the level L at the time when entry
COUNT DOWN returns on the level L
and which the meter is with state 0.
With the following transition from L to H of entry COUNT DOWN. Exit BORROW passes by again on the level H, thus generating an impulse which allows décrémenter of a unit the following meter.
It is possible to mount several meters in cascade.
It is enough to connect entries COUNT UP and COUNT DOWN of each meter to the exits CARRY and BORROW of the preceding meter. This is presented at figure 26.
10. - NINTH EXPERIMENT : ELECTRONIC PLAY
CARRIED OUT WITH A METER
With an aim of familiarizing you with the use of the meters, you now will carry out an assembly which simulates a set of Des. the goal of this play is to guess the state on which a meter stops.
10. 1. - REALIZATION OF THE CIRCUIT
a) Remove the connections relating to the preceding experiment and leave in place the integrated circuit MM 74C193.
b) Insert the integrated circuits MM 74C85, MM 74C08 and MM 74C32 on the matrix, as indicated in the figure 27-a and carry out the connections illustrated by this same figure.
Check that wiring carried out corresponds well to the electric diagram of the figure 27-b.
c) Lay out the first generator of clock on the frequency of 1 Hz and the second generator of clock on the frequency of 1 kHz.
10. 2. - OPERATIONAL TESTS
a) Energize the digilab.
b) Press on the P0 button during a certain time : the clock signal of 1 kHz increments the meter.
This one thus changes state thousand times a second. Slacken then P0. Thus, the meter stops in a random way on one of its 16 possible states.
c) Position the four switches in the state where you suppose that the meter stopped.
For example, if you think that the meter stopped on state 10, put SW0 on position 0, SW1 out of 1, SW2 out of 0 and SW3 out of 1 (see the table of figure 11).
d) Support on P1 : if the combination formed by the four switches represents a number lower than that which is determined by the state of the meter, the LED L0 will ignite.
This occurs for example if the meter stopped in a state representative of number 10 and that you composed one of the numbers ranging between 0 and 9.
So on the other hand, the number that you composed is higher than that given by the meter, the LED L4 will ignite.
This occurs for example if the meter stopped in a state accounting for 10 and that you chose a combination ranging between 11 and 15.
So finally the selected state is equal to that of the meter, the two LED L0 and L4 will flicker at the frequency of 1 Hz.
You can continue the experiment several times of continuation.
e) Put not under tension the digilab.
The tested assembly functions in the following way :
While supporting on P0, one frees the door OR (located by the letter “a” on the figure 27-b). Thus, the clock signal of frequency 1 kHz increments the meter. This one thus counts the impulses and stops when P0 is slackened. The frequency of counting being raised, one cannot envisage the state where the meter will stop.
The circuit MM 74C85 compares the state of the meter with the state made up on the four switches.
While supporting on P1, one frees the first three doors AND. Thus, the exit of each one of these doors recopies the level present on the exits of the comparator.
If the exit A > B is on the level H, it forces the door OR located by the letter “b” on the level H and the LED L0 ignites.
If the exit A < B is on the level H, it forces the door OR located by the letter “c” on the level H and the LED L4 ignites.
So on the other hand, the exit A = B is on the level H, the door AND located by the letter “d” validates the signal of frequency 1 Hz. The two doors OR “b” and “c” not being forced at the logical level H, the signal of frequency 1 Hz is found consequently at the exit of these doors.
The two LED L0 and L4 thus flicker at the same frequency of 1 Hz.
Thus this practice finishes in which you tried out the operation of the asynchronous and synchronous meters. Those have their exits coded into normal binary.
In the next practice, you will see how one translates this binary code into decimal code.
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