Designing a 16-4 priority encoder from 2 74148 8-to-3 line priority encoder device

Discussion in 'Homework Help' started by hitmen, Mar 16, 2009.

  1. hitmen

    hitmen Thread Starter Active Member

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    Hi all,

    My tutor gave me an answer I did not understand.
    I searched the datasheet of 74148 but it did not specify what is GS, E0 and E1.

    I also do not understand why the E1 of one 74148 is connected to the E0 of another.

    Can anyone help?
  2. beenthere

    beenthere AAC Fanatic!

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    All you have to do is look at the truth table to see what conditions set GS low and EO low. You can also see the effect of the EI^ input (hint - when it is high, what happens to the outputs, including GS^ and EO^?).
  3. hitmen

    hitmen Thread Starter Active Member

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    Well, I got the answer from my tutor but there is one thing I dont understand. What does GS stands for?

    I learnt from my tutor that:

    1) The IC that displays the MSB have to be disabled if it is below a certain level.

    2) The outputs from each gate have to be AND together to produce the desired output.

    I know that E is enable while I0 to I7 are the inputs while thost starting with A are the outputs.
    And I still dunno what GS stands for? :confused:
  4. thatoneguy

    thatoneguy AAC Fanatic!

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    GS is "Group Output" - goes low on priority detect, with priority address in A0-3, also active low, combined with GS to flag which IC when cascading two.
  5. beenthere

    beenthere AAC Fanatic!

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    Googling "74148" will let you find a data sheet for the device.
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