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LMK04828: SYNC/SYSREF_REQ Setting Sequence

Alice57
Intellectual 1730 points
Part Number: LMK04828


Hello Team,

I'd like to configure the SYSREF through SYNC/SYSREF_REQ pin. Without below three setting, is there any other settings are more needed? 

1. 0x16A[6] = 1 ; Set SYSREF_REQ_EN = 1

2. 0x139[1:0] = 2 ; Set SYSREF_MUX = 2 (pulser)

3. Toggle SYNC/SYSREF_REQ pin

Best regards,

Alice

  • 0
    TI__Mastermind 28590 points
    Hello Alice,

    Please also ensure the SYSREF pulser is powered up, SYSREF_PLSR_PD (0x140[0]) = 0

    And as always, because SYNC/SYSREF are shared, but sure to disable the SYNC to the dividers with SYNC_DISSYSREF = 1 and SYNC_DISX = 1. Where X is even clock dividers to mask off.

    73,
    Timothy
  • 0 in reply to Timothy T
    TI__Intellectual 1730 points

    Hi Timothy,

    I have one more question. When the SYNC/SYSREF_REQ is asserted, pulsed SYSREF is comes out. If I set the pulsed SYSREF counter as 5, only 5 pulsed SYSREF is comes out and then stop. At that time, do I must un-asserted the SYNC/SYSREF_REQ pin?

    Best regards,

    Alice

  • 0 in reply to Alice57
    TI__Mastermind 28590 points
    Hello Alice,

    That sounds more like pulser behavior. You should get output pulses as long as the SYNC/SYSREF_REF pin is high.
    Set SYNC_MODE, R323[0:1] = 0x00 (SYNC Pin Disabled). Does that solve your issue?

    73,
    Timothy
  • 0 in reply to Timothy T
    TI__Intellectual 1730 points
    Hi Timothy,

    SYSREF request through SYNC/SYSREF_REQ pin is only support continuous SYSREF? Could customer set SYSREF pulser mode when customer using SYNC/SYSREF_REQ pin for SYSREF request?

    Best regards,
    Alice
  • 0 in reply to Alice57
    TI__Mastermind 28590 points
    Hello Alice,

    The SYNC/SYSREF_REQ pin supports multiple modes....
    If you are using the pulser, you will be able to generate 1, 2, 4, or 8 pulses. Then request again by toggling the pin if you configure for pin mode. Maybe this better answers your question above.

    Table 1 of the datasheet shows some of the possible configurations for SYNC/SYSREF configurations.

    73,
    Timothy