Ozone debugger 3.20e debugging self-modified code problem

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    • Ozone debugger 3.20e debugging self-modified code problem

      Hi Segger,

      1. Thanks to the great Ozone debug, it helped a lot in development

      2. I want to report some problem about self-modified code. The application looks like this
      - My application implemented some check-sum against STM32's UUID
      - I added some code (store in 0x08008000) to calculate the checksum, and store result to somewhere in Flash
      - The code to calculate checksum is only executed one time. Once the check-sum is written to Flash, I used STM32 API to erase the code in 0x08008000
      - Assume FW will be read-out eventually, the approach adds some protection more or less

      3. I was using OZone debugger to debug the application. I opened a memory windows in 0x08008000
      After manipulating the registers to erase Flash, I expect to see the memory content becomes 0xFFFFFFFF. However, the values still kept in the window
      I even manipulate the FLASH control registers directly to *try* many PM regions
      With many many times trial, finally I disconnect the target and re-attach, the memory become 0xFFFFFFFF (erased status)

      4. I think this might relate to OZone implementation: you probably don't expect that users would "erase" the PM (or this is NOT common behavior)
      Therefore, the memory window content doesn't refresh. (need disconnect, re-attach, and the Ozone will re-read the memory)
      I'm just wondering, whether it's possible to force OZone to re-read the memory unconditionally to make such debug easier

      Thanks :)

      Regards,
      Lihgong
    • Hello Lihgong,

      Thank you for your inquiry.
      This behaviour is expected as J-Link will cache Flash contents to speed things up.
      You can disable Flash caching with command strings:
      wiki.segger.com/J-Link_Command_Strings#SetAllowFlashCache

      How to use them in Ozone is explained here:
      wiki.segger.com/J-Link_Command…ng_J-Link_Command_Strings


      Best regards,

      Nino
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