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TMS570LS3137: Termination of nTRST signal

Nilesh Khupase
Intellectual 470 points
Part Number: TMS570LS3137
Other Parts Discussed in Thread: TMDS570LS31HDK,

Dear Sir/Madam,

In TMS570, on nTRST signal there is a fixed internal pulldown which is in opposite to IEEE 1149.1 requirement. This pulldown will hold the internal JTAG controller in RESET state, until the reset signal is not driven by an external source. Is my assumption right? and What was the purpose behind such an implementation of the JTAG controller?

Whereas in Hardware Developement Kit external pullup resistor is connected on the nTRST line, is it OK?

Thanking you in advance. 

  • 0
    TI__Mastermind 21425 points

    Hello,

    As you mentioned the purpose of the pull-down is to hold the internal JTAG logic in reset.

    Regarding HDK nTRST circuitry, please take a look at these threads:

    TMS570LS3137-EP: Driving the nTRST pin
    Resolved
    Part Number: TMS570LS3137-EP Hello- I have a question on connection of the nTRST signal. The evaluation board for the part (see http://www.ti.com/tool/tmds570ls31hdk has a FET (see schematic page 7,…
    By in Space & High Reliability (Read Only) > Space & High Reliability Forum (Read Only)
    2 replies
    Latest by

    Best regards,
    Miro

  • 0 in reply to Miro
    Intellectual 470 points

    Hi Miro,

    Thank you for your reply. What benefit will it have to keep the JTAG logic in reset state during normal operation of the IC ?

    This is not mentioned in the threads you shared above.

    Best Regards.

       

  • 0 in reply to Nilesh Khupase
    TI__Mastermind 21425 points

    Hello,

    nTRST pulled down will keep TAP and debug logic in reset and this will prevent MCU to enter in debug mode while powered up. The pull-down makes sure that nTRST is asserted and the device will never enter debug in error.

    Best regards,
    Miro