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CCS/TMS320F28062: What to do with CSM section when using multiple applications in Flash

Olovskos
Intellectual 420 points

Part Number: TMS320F28062

Tool/software: Code Composer Studio

Hello again,

I have 2 applications running on the F28062. The first is a custom bootloader in FlashA and the other is the main application running in FlashB.

Both have to be secured with the CSM so both have the same 128bit CSM Key. But here is the question:

When I compile both of the Projects, should only one of the Projects specify the CSM section and what to do with it or can both change this section since they use the same key?

When I think about this, I would say that only the bootloader has to secure the Flash since it is the only program that changes the flash so I could omit the CSM password in the main application right?

So what would be the best solution for this?

And if I only use the CSM in the Bootloader, is it Ok to only delete the CSM section in the main applications linker file or would this lead to undefined behavior? What should I do with the CSM section in the linker file?

Thanks in advance :)

  • 0
    TI__Guru** 116081 points
    Hi,

    Boot loader will be programmed once and with assumption that you'll not change the security setting later, you can just include this in Boot loader and in main application link cmd file have CSM section define as TYPE = DESECT (below is example for reference) -

    reset: > H0SARAM PAGE 0, TYPE = DSECT

    Regards,

    Vivek Singh
  • 0 in reply to Vivek Singh
    Intellectual 420 points
    So when the bootloader jumps to the main application that runs out of secured flash there will be no problem? I will not have to do a csmUnlock() in the main application?
  • 0 in reply to Olovskos
    TI__Guru** 116081 points

    Since bootloader as well as main applications are running from secure flash, both have same privileges so there is no issue.  In general you never have to use csmUnlock() for running the code. 

    Vivek Singh

  • 0 in reply to Vivek Singh
    Intellectual 420 points

    Ok, thank you :)

    Just to be perfectly clear, when building the main application I want BOTH sections "csm_rsvd AND csmpasswds" to be DSECT so both of them won`t get touched while flashing new main application right?

    csm_rsvd            : > CSM_RSVD,   PAGE = 0, TYPE = DSECT
csmpasswds       : > CSM_PWL_P0, PAGE = 0, TYPE = DSECT

CSM_RSVD    : origin = 0x3F7F80, length = 0x000076     /* Part of FLASHA.  Program with all 0x0000 when CSM is in use. */
CSM_PWL_P0  : origin = 0x3F7FF8, length = 0x000008     /* Part of FLASHA.  CSM password locations in FLASHA */

    The csm_rsvd tells the DSP that the CSM is active so only the bootloader will set these values to 0x0000 when it is burned and the main application will NEVER change these so I declare csm_rsvd as DSECT in the main application, right?

    The csmpasswds stores the Password so again only the bootloader changes these values when it is burned and the main application should NEVER change these so I also declare csmpasswds as DSECT in the main application, right?

    Thank you

  • 0 in reply to Olovskos
    TI__Guru** 116081 points

    Hi,

    The csm_rsvd tells the DSP that the CSM is active so only the bootloader will set these values to 0x0000 when it is burned and the main application will NEVER change these so I declare csm_rsvd as DSECT in the main application, right?

    The csmpasswds stores the Password so again only the bootloader changes these values when it is burned and the main application should NEVER change these so I also declare csmpasswds as DSECT in the main application, right?

    Yes, that is correct.

    One clarification that csm_rsvd address range alone being 0x0 does not tell that DCSM is active. CSM gets active when CSM PASSWORDS are programmed and in that case it is recommended to programed the csm_rsvd space with data 0x0.

    Regards,

    Vivek Singh