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TCA7408 GPIO pull-up/-down

Henry Wang2
Prodigy 160 points

Hi Sir,

May I know when I settng TCA7408 GPIO port as input, is it need to add Pull-up/-down resistor?

I got float status on GPIO port during POR and see the INT# on low level, so my main system can't to working.

  • 0
    TI__Genius 16510 points
    Hello Henry,

    Are you asking if your GPIO port must have a pull up or pull down resistor externally if configured as an input?

    No, there is a register that configures the input pull up and pull down status.

    Upon startup, the default is that pull up resistors are enabled on inputs.

    Is there something causing the input to change and causing an INT to happen?
  • 0 in reply to Jonathan Valdez
    Prodigy 160 points

    Hi Jonathan,

    Why I got the INT# is low level during system power on? this INT# will effect my system can't boot-up.

    VccI=1.8V, VccP=3.3V, RST# & INT# both pullup 10KOhm.

  • 0 in reply to Henry Wang2
    TI__Genius 16510 points
    Henry,

    The INT upon startup is used to request the controller to set up the TCA7408 device.
    Please see page 7 of the datasheet: Register 01h – Device ID and Control
    "The Device ID and Control register contains the manufacturer ID and firmware revision. The Control register
    indicates whether the device has been reset and the default values have been set.
    • The Reset Interrupt is set B1=1 when the device is either reset by the RESET pin, a power on reset, or
    software reset.
    • Reset Interrupt is then cleared after being read by the master.
    • Writing to B7–B1 has no effect on these bits in the register.
    • A software reset is issued when the master writes B0=1.
    • When reading from B0, the value read will always be 0"

    If you hold RST low during powerup, the INT pin should be released and allowed to be pulled high.