74LS 3-STATE Octal Bus Transceiver. General Description. These octal bus transceivers are designed for asynchro- nous two-way communication between. The 74LS is a bidirectionnal bus transceiver with 3-state output. bits flow trough its 8 bidirectionnal buffers (G* held high) or disconnect from the Apple data. Texas Instruments 74LS Logic – Buffers, Drivers, Receivers, Transceivers parts available at DigiKey.

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Forms maths Geometry Physics 1. To carry out the experiments envisaged in this practice, it will be necessary for you to use the following material: At boundaries 2, 3, 4, 5, 6, 7, 8 and 9 can be connected eight lines of A1 to A8and eight others can be connected to pins 18, 17, 16, 15, 14, 13, 12 and 11 of B1 with B8.

You can notice the sign represented inside each buffer ; it indicates that the buffers used comprise a circuit of re-arrangement of the trigger type of Schmitt. Will finally know that the circuit 74LS is a circuit of technology T.

L and that, for this reason, it must be fed with a stable tension of 5 V.

A higher tension could damage it. It must be in position OFF at the time of its connection on the sector. Carry out then the connections necessary. The figure b represents the diagram of the electric circuit carried out. In this first phase, you will check the operation of the one of the eight bidirectional buffers of the integrated circuit. L0 and L1 flicker 74ls24 at the rate of 10 Hz.

Indeed, when SW0 is in position 1the passage of the signal in the direction of A8 with B8 is authorized. This is due to the fact that the exit of door 2 of figure 15 is at the high level whereas that of door 1 is on buffwr bottom grade thus prohibiting the B8 direction towards A8. Indeed, L0 still flickers, ordered by the signal coming from CP1 ; on the other hand L1 does not flicker any 74lx245. It presents a luminosity weaker than the normal. L1 ignites with its full intensity.


Digital buffer

You thus noted that L1 can be ordered independently of the buffer which, not validated, does not intervene. Now reverse the direction of transmission by applying the rectangular signal 74ls254 by CP1 to the B8 entry. Observe what occurs on A8. Rock then SW1 on position 0 to validate the circuit again. To check if the signal goes indeed from B8 towards A8repeat the same procedure as for the preceding case.

You have just checked the two directions of transmission of the signal between A8 and B8 of the one of the eight ways of the integrated circuit.

Adopt the same procedure for the seven other ways in order to check correct operation. By basing you on the results obtained, you can build the table of operation of the bidirectional buffer indicated figure 17 which can be summarized schematically by figure To carry out the following experiments, it will be necessary to use a meter. In the preceding practices, you tried out various types of meters ; that that you will examine now is not different from the others as for its design, but it has the great advantage of containing 12 stages in a single integrated circuit.

It is about the CDbinary asynchronous meter with 12 bitswhose synoptic diagram is represented figure The stitching of this circuit is indicated on figure The door of entry NAND is followed of a trigger of Schmitt who is used to improve quality of the signal, then come two reversers which control the chain of dividers. The meter is incremented each time the entry f1 passes from the high level on the bottom grade, i. This is symbolized by a bubble placed on the entry f1 in figure The entry RESET gives the meter to zero, it is asynchronous ; as soon as a level H is applied to him, the meter passes to 0.

The meter can go from 0 to 2 12 positions. The electric diagram of the circuit carried out is represented figure b, while the figure c represents its synoptic diagram. On the twelve exits of Q1 with Q12one finds a number binary of twelve bits active of: The most significant bit M. After the sixteenth clock pulse, the incrementing of the indication of the bill-posters starts, this one being in hexadecimal code, of 00 to finish to FF at the end of counting.


By observing the LED and the bill-posterscheck the correct operation of the meter by consulting the table of figure Of course, it is not a question to hope the clock pulses up to to check the table: By commenting on the experiment, one can say that each stage of the meter carries out a division by two of the frequency of the signal applied to its entry ; if one injects the signal with 10 Hzcoming from contact CP1at the entry f 1 of the meter, the various exits, one obtains signals whose frequency is each time reduced by half.

The table of figure 23 indicates the frequency and the period of the signals of the various stages of the meter and summarizes the test results. As you can note it, the frequencies spread out of 5 Hz with 0, Hzi.

It is thus enough to a little attention to observe the phenomenon and if there would remain some points obscure, do not hesitate to start again several times the experiment. Click here for the following lesson or in the synopsis envisaged to this end. High of buffrr Preceding page Following page.

Digital buffer – Wikipedia

Operational test of a Meter on 12 floors. Return to the synopsis. To contact the author. Static page of welcome.

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