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Cortex-M3 Flash Patch

citykid1
Note: This was originally posted on 9th December 2009 at http://forums.arm.com

I have been working with Keil uVision 4 and have been trying to figure out how to use the Cortex-M3 "Flash Patch" feature to map a contstant value to RAM.    I can't seem to find any information on how to do that.   

There are all sorts of press releases describing the FPB unit and its features but how do you access the flash patch feature from within Keil uVision?

Anyone had any luck with this feature?
  • Note: This was originally posted on 10th December 2009 at http://forums.arm.com

    Anyone had any luck with this feature?

    Yes. Besides having to program the appropriate FPB registers you'll also have to think of how to set up an appropriate infrastructure in your application. How does the application know whether or not to enable the FPB after reset, etc. Perhaps if you'd provide more more information about what you are trying to do, I could give you some hints.

    There is no difference here between Keil and any other tool chain.

    Regards
    Marcus
  • Note: This was originally posted on 10th December 2009 at http://forums.arm.com

    Yes. Besides having to program the appropriate FPB registers you'll also have to think of how to set up an appropriate infrastructure in your application. How does the application know whether or not to enable the FPB after reset, etc. Perhaps if you'd provide more more information about what you are trying to do, I could give you some hints.

    There is no difference here between Keil and any other tool chain.

    Regards
    Marcus



    Hi Marcus,

    Thanks for the feedback.     I have seen the progrmmers model for the FPB system,  I assumed that there would be some convenient way in the Keil uVision environment to utilize this feature.    In other words,  have it somewhat automated for the end user  (i.e. like setting a watch variable,  etc...).    It appears that this is a manual operation for now.       It would be so nice to have a feature where you could point to an instruction or operand and have it easily mapped to ram.

    Best Regards,

    Ed
  • Note: This was originally posted on 10th December 2009 at http://forums.arm.com

    Thanks for the feedback.     I have seen the progrmmers model for the FPB system,  I assumed that there would be some convenient way in the Keil uVision environment to utilize this feature.    In other words,  have it somewhat automated for the end user  (i.e. like setting a watch variable,  etc...).    It appears that this is a manual operation for now.       It would be so nice to have a feature where you could point to an instruction or operand and have it easily mapped to ram.

    FPB is not responsible for watching variables -- only for redirecting instructions and literals. You cannot redirect arbitrary data access since FPB does not affect the data side of the processor bus. Besides setting breakpoints, FPB can be used to "replace" instructions. A branch to an erroneous function (rather, the first instruction of that function) could be replaced with a branch to a fixed function that has been installed in some writable memory through an upload mechanism.
    While I could perhaps imagine use cases, this is not primarily something that you would do interactively. I suppose you could also write a macro for MDK's debugger which programs FPB as a workaround.

    Again, what were you thinking of specifically?

    Regards
    Marcus