Need help multiplexing EUSART output

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  1. - 6th April 2008, 23:42 #1
    Charles Linquis's Avatar
    Charles Linquis
    Charles Linquis is offline Prolific Poster
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    I have successfully used a 74HCT125 for this purpose. You can selectively enable each gate to drive what you want. If you add a pull up on the output of each gate, you can "idle high".
    One package (two gates for TRANSMIT, two devices for RECEIVE) plus an inverter will allow you to use one pin to select which device you want to "speak to".

    Connect PIC TXD to the inputs of two gates (call them A & B) Connect the output of A to
    device 1, connect the output of B to device 2.

    Connect the outputs of gates C & D to the PIC RXD. Connect the input of C to device 1 and the input of D to device 2.

    Connect the ENABLES of gates A and C together, and the ENABLES of B & D together.

    Put an inverter between the pairs of enables. Drive the input of the inverter from a PIC pin.
    Charles Linquist
  2. - 6th April 2008, 23:56 #2
    mister_e's Avatar
    mister_e
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    How about my favourite STG3157? ok ... a bit much expensive i agree...
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.
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