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SCANSTA112: High-Z Mode for JTAG pins

Don Schelle
Expert 4150 points
Part Number: SCANSTA112

Hello,

I have an application where I want to take JTAG channel 3 signals to high-Z when in mission mode.  Is there a hardware pin to control that or is it a register control only?

Don

  • 0
    TI__Guru*** 140055 points

    Don

    The TDIB, TMSB, and TRSTB inputs have a 25KΩ pull-up resistor to VDD. When the device is powered off (VDD floating), these inputs appear to be a capacitive load to ground. When VDD = 0V (i.e. not floating but tied to VSS) these inputs appear to be capacitive with the 25KΩ pull up resistor in parallel with the capacitor to ground. The TCKB input has no pull-up resistor. When the device is powered off (VDD floating), the input appears to be a capacitive load to ground. When VDD = 0V (i.e. not floating but tied to VSS) the input also appears to be a capacitive load to ground.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 4150 points

    Thanks David,

    I think you misunderstood my question.    When SCANSTA112 is powered on, is there a way, via a hardware GPIO pin, to force port 3 JTAG pins into a High-Z state?

    We believe that this can be done via a software interface, but are unsure if a simple I/O pin is available.

    Don

  • 0 in reply to Don Schelle
    TI__Guru*** 140055 points

    Don

    Unfortunately, there is no way to force port 3 JTAG pin into the high-Z state.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Mastermind 43795 points

    Hi Don,

    The OE pin can force the Local Scan Ports of the STA112 into a Tri-State or Hi-Z condition.  Unfortunately this pin works on all the ports, not just port 3.

    Regards,

    Lee