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LMX2594: Sometimes the reset operation fails

user5788058
Intellectual 410 points
Part Number: LMX2594
Other Parts Discussed in Thread: USB2ANY

Hi,

We are currently starting up a PCB equipped with LMX 2594.
I have two questions.

First, when I turn on the power and read back with SPI, all registers return 0x0000.
Although page 39 of the datasheet explains that this device has a power-on reset feature, I am confused because it does not appear to work.
This happens every time the power is turned on.

Second, the software reset sometimes feels like it doesn't work.
We use an oscilloscope to verify that the SPI communication from our equipment to this device meets the timing specifications described in the data sheet. The program is executed according to the program sequence described in the data sheet. However, even if all register settings are completed, the set frequency is not obtained and the register readback is 0x0000.

This means that the condition mentioned in the first question, that all registers appear to be set to 0x0000 after power on, has not been resolved after the soft reset.

This doesn't happen all the time, and it happens occasionally, so I don't know how to deal with it.

Is there any knowledge that could be helpful?

  • 0
    TI__Mastermind 27981 points

    Hi,

    Could the device somehow be in Lock Detect mode.  For the readback, the MUXOUT_LD_SEL should default to readback, so this should read back.

    However, sometimes when programming, it is popular to set this pin to "Lock Detect".  As lock detect and Readback share the same pin, ensure that it is not related to this.  Note that register R0 has FCAL_EN and is programmed last, but also contains MUXOUT_LD_SEL, which maybe it is being changed on the R0 write.

    Also, although not required, it is best to toggle the RESET bit as a software reset.  Although the POR does a register reset, there are state machines and doing this gives the most consistent result.

    Regards,
    Dean

  • 0 in reply to Dean Banerjee
    Intellectual 410 points

    Thank you for an answer.

    Registers are set in the following order.
    R0: 0x0002
    R0: 0x0000
    R112 to R1
    R0: 0 x 6410
    R0: 0 x 6418
    In the above procedure, it seems that the MUXOUT _ LD _ SEL is not set to the Lock Detect.
    I will check the SPI communication circuit again. If my device is in Lock detect mode, I have to assume a faulty SPI communication circuit.

  • 0 in reply to user5788058
    TI__Mastermind 27981 points

    Hi,

    If you are using our EVM with TICSPro, then you can do readback with the USB2ANY (or Reference Pro board).

    If you are doing your own software, maybe there is something you missed, such as setting the Read/Write bit.  There are really 7 address bits and then the 8th bit is really the R/W bit.

    Regards,
    Dean