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DS90UB953A-Q1: REMOTE_BIST_CTRL register settings

Abhishek Hegde
Prodigy 60 points
Part Number: DS90UB953A-Q1


In https://www.ti.com/lit/ds/symlink/ds90ub953-q1.pdf, BIST_CLOCK [2:1] in REMOTE_BIST_CTRL (0x14) has following description

BIST clock source selection.
00: External/System clock
01: 50 MHz internal clock
1X: 25 MHz internal clock
Also following Clocking Modes were described in section 7.4.1, some of which I have mentioned below.
1. Synchronous clock
2. Non-Synchronous external clock
3. Non-Synchronous internal clock
..

Would you please explain based on what BIST_CLOCK must be configured ? and whether it's limited by Clocking mode configuration described above ?
  • 0
    TI__Expert 6345 points

    Hello Abhishake,

    Thank you for reaching out with your question. Please allow me 1-2 days to get back.

    Best Regards,

    Shruti

  • 0 in reply to Shruti More
    TI__Expert 6345 points

    Hello Abhishake,

    Thank you for your patience!

    The picture below shows register description of register 0xB3 in the DS90UB954 datasheet.

    It states that "This register field selects the BIST Clock Source at the 953 Serializer. These register bits are automatically written to the CLOCK SOURCE bits (register offset 0x14) in the Serializer after BIST is enabled. See the appropriate Serializer register descriptions for details."

    So, depending on the clock source and clocking mode you are using in your system, you can select the appropriate BIST clock source. 

    For more information, please see section 3.2 BIST in this app note: https://www.ti.com/lit/an/snla267a/snla267a.pdf

    We also have this BIST training video online: https://training.ti.com/diagnostics-status-monitoring-data-protection-and-built-self-test-bist 

    Hope this helps.

    Best Regards,

    Shruti

  • 0 in reply to Shruti More
    Prodigy 60 points

    "depending on the clock source and clocking mode you are using in your system, you can select the appropriate BIST clock source"

    Can you elaborate on this. an example would be much appreciated.

  • 0 in reply to Abhishek Hegde
    TI__Expert 6345 points

    Hello Abhishek,

    The BIST clock frequency is controlled by the BIST_CLOCK_SOURCE field in the BIST Control register. This 2-bit value will be written to the Serializer register 0x14[2:1]. A value of 00 will select an external clock. A non-zero value will enable an internal clock of the frequency defined in the Serializer register 0x14.

    For example, if your system is operating in the synchronous mode, you would set 0xB3[2:1] and 0x14[2:1] as 1X (25MHz internal clock).

    You can find out more information about all the operating modes in section "7.4 Device Functional Modes" in the DS90UB953 and DS90UB954 datasheets. 

    Best Regards,

    Shruti

  • 0 in reply to Shruti More
    Prodigy 60 points

    Hello Shruti,

    I can understand the register description. What I want to know is how to decide the source for BIST_CLOCK. What are the implications of my choice. How does it affect the overall system.

    Say if I have chosen Synchronous clock mode. Can I choose any of the three sources for BIST_CLOCK or should it be 25MHz internal clock only.

  • +1 in reply to Abhishek Hegde
    TI__Expert 6345 points

    Hello Abhishek,

    Thank you for clarifying your question. 

    Usually you run BIST “at speed” meaning that the frequency that the application would be running at in order to emulate the data path that you would have in normal use case. To do this, usually an external clock is used. If you are using 953 in synchronous mode, the "external clock" is the back channel clock from 954. If you are using 953 in non-sync mode, the "external clock" is the CLKIN to the 953.

    We recommend always using external clock with BIST.

    Best Regards,

    Shruti