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SCAN921226 SCAN921025 JTAG

Conrad
Prodigy 100 points

If we are using the JTAG on the SCAN921025HSM and SCAN921226HSM, what should we do with the pins?

  • 0
    TI__Mastermind 29635 points
    Hi Conrad,

    Unfortunately, we do not have a wealth of knowledge regarding this part, due to its relative age. I will answer as best as I can.

    Regarding the JTAG pins, if you choose to use them, it is common to have a pull-up (or pull-down) resistor (10 kOhm is a typical value) on the TDI/TDO/TMS/TRST/TCK signal pins to prevent floating JTAG signals. If the pull-up (or pull-down) is supplied elsewhere on the same net, then you may not need to provide this additional 10 kOhm resistor.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Prodigy 100 points
    From the DataSheet
    TDI Test Data Input to support IEEE 1149.1. There is an internal pullup resistor that defaults this input to high per IEEE 1149.1.
    TDO Test Data Output to support IEEE 1149.1
    TMS Test Mode Select Input to support IEEE 1149.1. There is an internal pullup resistor that defaults this input to high per IEEE 1149.1.
    TCK Test Clock Input to support IEEE 1149.1
    TRST Test Reset Input to support IEEE 1149.1. There is an internal pullup resistor that defaults this input to high per IEEE 1149.1.

    Does this mean I can leave unconnected?
  • 0 in reply to Conrad
    TI__Mastermind 29635 points
    Hi Conrad,

    Yes, you should be able to leave those pins unconnected due to the internal resistance. I am unsure of what the internal pullup resistor value is, but if it is similar to other SCANSTA parts in our portfolio, then the value is in the neighborhood of about 25 kOhms. You can verify the exact value of the pull-up resistor with an ohmmeter.

    Thanks,

    Michael