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LMK04828: Question: are the registers locked to spi write after power up or Is there a typo in LMK datasheet

arye nudelman
Intellectual 255 points
Part Number: LMK04828

Please see the attached picture to the reference from datasheet, as i understand the defult after power is that all registers are locked to spi write?

does it mean that the first register to be written is 0x1FFF with 0x0 to unlock all other registers to spi write option?

can we send each spi command once or we need few times as i saw in some spi logs of others 

if i'm wrong in my above conclusion regarding locked register to spi write, can i use the next squence to read the product id from register 0x03?

0x000090

0x000010

0x000200

0x014A33

0x800300

i want to see the response of 0x06 on the RESET GPIO, is this squence right? cause now working with the EVB and sending this SPI squence not from the gui but from my implemented MCU it not gives me the 0x06 response

  • 0
    Intellectual 255 points

    sorry i would like to add that now i understand that if written in 0x1FFF 0x83 it means that all registers unlocked, but why the gui and some logs of writing to lmk ends sometimes with writing to 0x1FFF 0x53, what does it mean 0x53 and not 0x83? why it needed to write to this registers during init if they are defualt ? why i saw that the gui writes to registers 0x03 till 0x06 if for example 0x03 is readonly register? do we must to write to it?

  • +1 in reply to arye nudelman
    TI__Mastermind 33710 points

    0x53 hex is 83 decimal.

    TICS Pro is not very clever about how it stores and writes registers. TICS Pro's "write all registers" function writes every register in the raw registers page, in order, from top to bottom, every time. There's no attempt to detect if some registers are modified from defaults or to skip unmodified registers. There's no attempt to mask or omit read-only registers. Solely because we include read-only registers in the raw registers page for review, those registers end up being written whenever TICS Pro performs a "write all registers" behavior.

    In the future of TICS Pro, we plan to separate the presentation of registers in the raw registers page from the order in which they are written, which should hopefully resolve this kind of confusion. This includes skipping or omitting registers which are unmodified from defaults after a POR/RESET toggle, marking registers or fields within registers with the relevant access policy information (read-only, read-write, write-once-self-clearing, constant, etc), and generating exportable programming sequences that omit unnecessary register transactions.

    As for your application, if a register defaults to a value that matches your configuration value, you can skip it in nearly every case. A special exception is made for the register containing the LSBs of the N-divider, because writing the LSBs of the N-divider triggers VCO calibration - this must be written, usually after other initialization registers (to ensure the PLL/VCO are powered up). If you do not need to lock the register map for any reason, you can omit any register writes to the SPI_LOCK register.