74hc374 instead of 74hc373

Discussion in 'The Projects Forum' started by khanna_gunjan, Jul 13, 2006.

  1. khanna_gunjan

    Thread Starter New Member

    Jan 29, 2006
    8
    0
    Hi,

    by mistake i have bought 74hc374 instead of 74hc373.. and the software for this hardware is not possible to be changed.. is there any way that i can use 74hc374 at the place of 74hc373.. pls suggest.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    The answer to your question hinges on the timing of the signal your software is applying to pin 11 of the original 74HC373.

    As you can see from comparing the truth table of the two parts, the 373 uses a latch-enable signal to continuously enable the signals on the 8 input lines to pass through to the corresponding 8 output lines while the 374 uses a low-to-high edge to latch the data present on the inputs into the output latch. The 8 output lines on the 374 undergo a change only at the time of the low to high transition on pin 11. The 8 output lines on the 373 will follow changes on the input lines as long as a "high" level is applied to pin 11.

    A lot depends on how soon after your software latches the output on the 373 before it reads the output of the 373.

    In the end it all depends on how your software is driving pin 11 of the 373. Since the 373 latches the output on the high-to-low transition and the 374 latches the output on the low-to-high transition, You may need to introduce an inverting gate in the signal line being used to drive pin 11.

    One of our other members may be able elaborate on my interpretation.

    hgmjr
     
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
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