"TDO is constant high" error after Coresight detection on Cortex-A9 SOC

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    • "TDO is constant high" error after Coresight detection on Cortex-A9 SOC

      I have a Cortex-A9-based SOC (a Broadcom device) that produces the following error when hooked to a J-Trace Pro debugger:


      Source Code

      1. Device "CORTEX-A9" selected.
      2. Connecting to target via JTAG
      3. TotalIRLen = 4, IRPrint = 0x01
      4. JTAG chain detection found 1 devices:
      5. #0 Id: 0x4BA00477, IRLen: 04, CoreSight JTAG-DP
      6. Scanning AP map to find all available APs
      7. AP[0]: Stopped AP scan as end of AP map has been reached
      8. Iterating through AP map to find APB-AP to use
      9. Could not measure total IR len. TDO is constant high.
      10. Could not measure total IR len. TDO is constant high.
      11. ****** Error: Could not find matching AP in Coresight setup
      12. Could not measure total IR len. TDO is constant high.
      13. Could not measure total IR len. TDO is constant high.
      14. Cannot connect to target.
      Display All
      I've verified that things are connected correctly and that the SOC is indeed pulling up JTDO (not a stray pull-up or similar). Is this similar to this issue where the debugger is missing the right recipe for the device?
    • Hello,

      Thank you for your inquiry.
      Broadcom devices usually require special init steps when connecting which is why the generic Cortex-A9 as target device does not work.
      Is the chip you are using listed on our supported devices site?
      segger.com/downloads/supported-devices.php
      If yes simply select the correct device name when connecting.
      If not support must be added first. Could you name the exact target device you are looking to debug?

      How to add support to new devices yourself is explained here:
      wiki.segger.com/Open_Flashloader#Open_Flashloader

      Best regards,
      Nino
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