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problems with 74HC165 PISO Shift Register

Discussion in 'General Electronics Discussion' started by King_bob, Feb 8, 2014.

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  1. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    The following pins MUST have a valid logic level (i.e. not left floating)

    1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 14, 15.

    Regardless of how silly it might sound, they must have a valid input voltage or the chip could behave unpredictably.

    If the input pins are tied to the output of another chip that is capable of pulling the value both high and low (as an ATTiny can) then there is no need for pull-up or pull-down resistors as long as you maintain a valid logic level on these pins. If you ever plan on setting them up as inputs, you will need that pull-up or pull-down again.
  2. King_bob


    Feb 8, 2014
    ok, is there anyway to cheat it? so I dont have to use a resistor for each pin?
  3. mursal


    Dec 13, 2013
    Steve I think Bob has most of those pins under control, just a matter of checking pin 10 and pin 1.

    As long as you have it working, its easy to tweak it here and there a bit :)

    Happy days ..............
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Yeah, if they're not connected to anything else, just connect them directly to ground or +5V. You only need the resistor if you're connecting it to something else that needs to change the logic level.
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