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LMK04828: 4-wire SPI eregister settings for RESET/GPO (#5 pin)

Kazuhiko Hirano
Genius 14918 points
Part Number: LMK04828

Hello,

My customer would like to use 4-wire SPI and RESET/GPO pins as an open drain MISO.
The all required register settings are as follows?
Any other required register settings or anything they have to care about?
    - Register 0x000 bit#4(SPI_3WIRE_DIS) = 1b
    - Register 0x14A bit#5-#3(RESET_MUX) = 110b
    - Register 0x14A bit#2-#0(RESET_TYPE) = 110b

Best regards,

K.Hirano

  • +1
    TI__Guru** 107030 points

    Hi Hirano-san,

    Yes, these are the related registers. 

    After a Vcc power up, RESET/GPO is default to input with internal pull down.

    Since you would like to set this pin as open drain output, you will have an external pull-up resistor at this pin. 

    I think, after Vcc power up, this resistor will keep the device in reset status. We may need to, first of all, program the device to set this pin to open drain output, before continue program all other registers. 

    Even though we set this pin to open drain, output is still either 0 or 1, high-Z output is not supported. So I suggest use push-pull output instead of open drain. As such, we don't need the external pull-up resistor and therefore avoid confusion after Vcc power up.