Study of the operation of a
register with shift rebouclé on itself |
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Created it, 06/10/19
Update it, 06/10/28
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8. - FOURTH EXPERIMENT : OPERATIONAL TEST OF A DATA TRANSMISSION OF THE SYNCHRONOUS SERIES TYPE
In the preceding experiment, you noted how it is possible to charge a register and to shift its contents of it towards a single exit.
In this handling, you will charge in a circuit with shift of information relating to the state of eight entries, will transmit them on only one wire of connection and will find them all the eights in parallel on another register placed at the end of the line of transmission.
8. 1. - REALIZATION OF THE CIRCUIT
a) Remove matrix the integrated circuit MM 74C165 and all the connections relating to the preceding experiment.
b) Introduce on the matrix the integrated circuits MM 74C164 and MM 74C165 into the position indicated to the figure 36-a and carry out the connections illustrated by this same figure.
The figure 36-b shows the electric diagram of the circuit which you carried out.
As you can note it, the parallel entries of the register MM 74C165 are positioned on logical levels precise good.
The two registers are placed one beside the other for reasons of space and convenience. In reality however, they are very often far from the other for the remote control of information. You must thus imagine a rather long connection which goes from exit QH of the first register at entry A of the second.
Since the two registers are ordered by the same clock signal, it is necessary to lay out a second wire of connection which joins together two entries CLOCK : for this reason, the transmission is known as synchronous.
Often, one uses even two different clocks, for the transmission and another for the reception. In this case, it is the transmitted signal, itself, which synchronizes the reception. This type of transmission is known as asynchronous.
c) Introduce the card into the catch of the sector and energize the digilab.
d) Place SW0 on position 0. The register parallel-series functions then in mode LOAD and the levels present on the parallel entries are charged on the exits with the various rockers.
e) Temporarily put SW1 on position 0, then replace it on position 1 : the eight LED are extinct.
Indeed, as you can see it in the diagram of the circuit, you apply this way a level L to entry CLEAR of the register parallel series. All the exits thus pass on the level L ; the register is initialized or given to zero.
f) Commutate SW0 on position 1 : the register parallel-series is ready to function thus in SHIFT mode.
The current contents of the two registers are represented schematically on figure 37 (first line).
g) Support on P0 : L0 ignites. Indeed, the contents of the eighth rocker of the first register were transferred to the first rocker from the second register. All other information also shifted of a stage.
The first stage of the register parallel-series is charged by a level L since the entry series is connected to the mass (figure 37 - 2nd line).
h) Apply seven other clock pulses using the P0 button : with each clock pulse, you note a shift of a row towards the line of information, as that is represented on figure 37.
At this moment, all the contents of the first register were transferred in the second, which you note by observing the LED which are in the following situation:
Lit L0 Lit L4
Extinct L1 Extinct L5
Lit L2 Lit L6
Extinct L3 Lit L7
i) Continue to actuate P0 ; after eight clock pulses, all the LED are extinct.
The second register was indeed responsible for all the levels L which come from the entry series of the first register.
j) Put on “OFF” the switch of food and remove the card of the socket-outlet.
With this experiment, you checked the principle on which the transmission of information of the synchronous series type is based.
Logical information is transmitted by a “transmitting” circuit on only one wire thanks to a register parallel-series. They are received by a “receiving” circuit which is a register parallel series.
The first register takes information in parallel and one transmits them after the other in series, the second receives them one after the other and then simultaneously presents them in parallel.
Naturally, it is necessary to know the exact moment where information must be noted on the exits of the “receiving” register. In our case, we counted the number of the clock pulses applied to the circuit ; with the eighth impulse, you observed the exits of the second circuit and you ensured yourselves that they corresponded well to the entries of the first circuit.
Actually, this counting is made automatically by earth phantom circuits which announce that all information arrived, therefore available for the reading.
9. - FIFTH EXPERIMENT : STUDY
OF THE OPERATION OF A REGISTER A
SHIFT REBOUCLÉ ON ITSELF
With this handling, you will check how it is possible to store the information contained in a register at shift.
In the preceding experiment, you saw that the contents of the register parallel-series MM 74C165 were transferred in the register parallel series MM 74C164 and that after this operation, the register parallel-series had lost its contents.
During this experimentation, you will see how one can store the information on the place of transmission as on the reception point by rebouclant on itself the first register so that information circulates there permanently.
9. 1. - REALIZATION OF THE CIRCUIT
Modify connections of the circuit relating to the preceding experiment, as illustrated with the figure 38-a and specified below :
Disconnect mass the entries B
and F (pins 12
and 4) of the integrated circuit MM
74C165 and connect them to “+”.
Disconnect “+” the
entry E (pin 3)
MM 74C165 and connect it to the mass.
Disconnect mass the entry series (pin
10) MM 74C165 and connect it to
exit QH (pin 9).
With these new connections, you simply changed the logical levels applied to the parallel entries of the register parallel-series. Moreover, you connected his exit on its entry series as you can see it on the electric diagram of the figure 38-b.
9. 2. - OPERATIONAL TEST
a) Place SW1 on position 0, introduce the card into the socket-outlet and energize the digilab : all the LED are extinct since entry CLEAR is activated.
b) Initially put SW0 on position 0, then on position 1 : you thus charged the register parallel-series. The contents of the two registers are indicated on the figure 39-a.
c) Put SW1 on position 1 and support on P0 : the LED L0 ignites.
d) Support seven other times on P0 : you note that the second register received all the contents of the first, which is indicated to you by the state of the eight LED.
Up to that point, very was held as in the preceding experiment. The current contents of the registers are shown with the figure 39-b.
e) Actuate P0 several times : you note that the LED do not die out as in the fourth experiment, but continue to ignite and to die out according to the shift of information.
Indeed, the first register preserves its contents, because its exit is rebouclée on its entry.
Now, instead of shifting information by means of P0, this one will be shifted automatically thanks to the clock signal provided by the oscillator of the digilab.
f) Cut off the supply by putting the switch on the position “OFF”.
g) Put SW0 and SW1 on position 0.
h) Modify connection between pin
2 (CLOCK) of the integrated
circuit MM 74C165 and the P0
contact by moving it on contact CP1 as
indicated on figure 40, where the preceding connection is represented in dotted
line.
i) Connect contact COM1 of the first generator of clock of the digilab with the contact located by inscription 10 Hz. (See figure 40).
Thus cabled, the generator provides a rectangular signal of frequency 10 Hz. This same rectangular signal, through contact CP1, is applied to entries CLOCK of the two registers ; in this way, the progression of information in the registers will not be ordered any more manually via the P0 button, but automatically by the impulses of the generator of clock.
j) Feed the digilab and put SW0 on position 1 : the first register is charged and the LED are extinct since SW1 is in position 0.
k) Put now SW1 on position 1 : the exits of the register parallel series are not forced any more with state 0. This register thus starts to take care and with each clock pulse, you see information shifting as lighting and the extinction testify some to the LED.
With the procedure described above, you can carry out the shift of any combination of lit or extinct LED. For that, it is enough to change the levels applied to the parallel entries and then to charge them in the register parallel-series.
In conclusion, this experimentation shows you how to store the information inside a register by simply connecting the exit to the entry.
Everyone knows the luminous inscriptions which ravel while being repeated periodically : the operation of the circuits with which these plays of light are carried out is based on the same principle as the registers with shift rebouclés on themselves.
In addition to those tested in this practice, there are other types of registers, described in a later theory, such as for example the dynamic registers.
In the next practice, you will examine the meters and the dividers of frequency.
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