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LMK04368-EP: 4-Wire SPI Interface

Avihay Froo
Prodigy 160 points

Part Number: LMK04368-EP

Tool/software:

Hi,

I want to have a 4-wire SPI interface, instead of the default 3-wire.

In this case, I understand that I should change Bit 4 of Register 0x000 to "1" (3-Wire Mode Disabled").

1.) Does SDIO (pin 52) changed to SDI (MOSI, input)?

2.) As SDO (MISO, ouptut / SPI Readback), I need to choose one of the following:

a. CLKin_SEL0 (pin 26) - Register 0x148

b. CLKin_SEL1 (pin 27) - Register 0x149

c. STATUS_LD1 (pin 63) - Register 0x14A

d. STATUS_LD2 (pin 16) - Register 0x15F

Am I correct?

Please advise,

Avihay

  • 0
    TI__Genius 11005 points

    Hello Avihay,

    I'll get back to you by the end of the week.

    Best,

    Andrea

  • +1
    TI__Mastermind 35330 points
    Avihay Froo said:
    Does SDIO (pin 52) changed to SDI (MOSI, input)?

    Yes, when 3-wire mode is disabled, SDIO is now SDI.

    Avihay Froo said:
    As SDO (MISO, ouptut / SPI Readback), I need to choose one of the following

    Partially correct. One of the listed pins should be selected, but your list is non-exhaustive and does not reference the correct registers for all pins. The list below is exhaustive (bolded includes any differences from your list):

    1. CLKin_SEL0 (pin 26) - Register 0x148
    2. CLKin_SEL1 (pin 27) - Register 0x149
    3. RESET/GPO (pin 37) - Register 0x14A
    4. STATUS_LD1 (pin 63) - Register 0x15F
    5. STATUS_LD2 (pin 16) - Register 0x16E

    Other trivia regarding SPI readback:

    • Setting 3-wire mode enabled does not prevent using the GPIO above from also acting as 4-wire readback pins. You can do both 3-wire and 4-wire SPI at the same time, if you so choose.
    • You can direct readback from multiple of the pins above at the same time, if for some reason you needed to do this (we sometimes do this for debug)
    • For SPI controllers operating at < 3.3V, all inputs are 1.8V-compliant, and the SDO in both 3-wire and 4-wire may be configured as open-drain.