LMK04828: LMK04828 SPI write sequence

jinfeng tao

Prodigy 130 points

Part Number: LMK04828

Hi TI expert

We have questions about the writting sequence of LMK04828 register:

The register of SPI LOCK[7:0] is written lastly, and the value of 83(dec) is written into SPI LOCK[7:0]

83: Register unlock

Why should the last register(SPI LOCK[7:0]) is written into the status of unlock?

what is the function of SPI LOCK[23:0]?

Thank you for your review and help.

over 5 years ago

0 Derek Payne over 5 years ago

TI__Mastermind 33710 points

Hello Jinfeng,

Think of SPI_LOCK registers as a write-enable control. By writing SPI_LOCK[23:0] != 0x000053, all registers except SPI_LOCK cannot be modified by the SPI bus. By writing SPI_LOCK[23:0] = 0x000053, all registers can once again be modified by the SPI bus. SPI_LOCK feature was requested by a customer during development, because their SPI bus was shared with other devices and they did not have enough chip-select outputs for all devices on the bus. For cases where each LMK04828 has a distinct chip select input, or if each LMK04828 shares the same register programming, SPI_LOCK feature is not necessary.

If you do not need the SPI_LOCK feature, you can skip writing these registers. The POR default settings allow all registers to be written normally.

Regards,

Clock & timing

Clock & timing forum

LMK04828: LMK04828 SPI write sequence