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AM6442: CCS debug without TRSTn? XDS200 with CM10 connector

Robert Finger
Genius 17497 points
Part Number: AM6442

Team,

Is it possible to debug AM6442 without TRSTn connection to the debugger?

A customer of mine has designed an ARM CM10 connector on his board. TRSTn ist not availble on it. When trying to use CCS and a XDS200 to get JTAG connection, CCS complains with an SC_ERR_PATH_BROKEN (-233) error. This was tested with bootmode "no boot". 

When they manually modify the JTAG adapter to connect TRSTn as well, debug access is working! Is there maybe any CCS setting to avoid the need for TRSTn?

Thanks,
  Robert

  • +1
    TI__Guru 63145 points

    They must connect the debugger TRSTn signal to the AM64x device since TI recommends an external pull-down on this signal to match the internal pull-down that is implemented on the AM64x input. This signal is pulled low by default to hold the JTAG TAP controller in reset until the debugger drives it high. This is done as another safety precaution to prevent noise from coupling into the JTAG port that accidently causes the Debug Subsystem to change code execution during normal operation. This approach has been used on TI processors for many years.

    Regards,
    Paul