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Is this IC active high or active low?

Discussion in 'Electronic Basics' started by Michael, Dec 29, 2003.

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  1. Michael

    Michael Guest

    Hi - on page 3 of the datasheet for the Holtek HT12E
    ( it says that A0-A7 have a "NMOS
    TRANSMISSION GATE PROTECTION DIODE (HT12E)" internal connection. Then it
    says "Input pins for address A0~A7 setting. These pins can be externally
    set to VSS or left open" So just to clarify - does that mean that when any
    of A0-A7 are left open it will be the equivalent of a "1" and when it is
    grounded it will be the equivalent of a "0"? So what would happen if I
    connected them to VCC? Thanks alot,

  2. You re-enforce the "1".

    | __O Thomas C. Sefranek
    |_-\<,_ Amateur Radio Operator: WA1RHP
    (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz
  3. Michael

    Michael Guest

    allright - that's what I thought - I just wanted to be sure. I'm putting
    one of these in a remote control for my house's outdoor lights. Since I'm
    aiming for it to be as small and lightweight as possible - I'm just going
    to put holes for jumpers to ground next to pins A0-A7 - that way I can set
    the code to whatever I want after I etch the PCB, but I won't have to deal
    with the weight and size of a dip switch. For the reciever unit of course
    I'll just probabaly use a normal dip switch.
  4. Ian Bell

    Ian Bell Guest

    I used this chip in a project earlier this year. I just used a DIL switch
    to connect A0-A7 to ground (Vss). There is no need for pullups as they
    have them internaly. There is therefore no need to connect them to Vcc but
    you should be able to drive them directly from a CMOS gate.

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