TMS320F28234: Low power mode error

Chandran,

Thanks for reaching out to the E2E.

Likely this is a result of the Code Security Module causing an intentional JTAG communications break if code is executed from a secure memory.  Even if you have not programmed a password(in default state of all 0xFFFF), you will still need to execute an initial read of the password key locations in your code to unlock the device.  This would need to be done once at power up/reset.  

If you look in our code examples you'll find a function called "CsmUnlock" that will take care of this.  In the case that you have programmed the CSM, you can also insert your unique password values in this function to unlock the device.  I've copied the function below in case you want to inline the reads quickly.

This section of the device TRM goes into more detail of the logic in play.

CsmUnlock()
{
    volatile Uint16 temp;

    //
    // Load the key registers with the current password. The 0xFFFF's are dummy
    // passwords.  User should replace them with the correct password for the 
    // DSP.
    //
    EALLOW;
    CsmRegs.KEY0 = 0xFFFF;
    CsmRegs.KEY1 = 0xFFFF;
    CsmRegs.KEY2 = 0xFFFF;
    CsmRegs.KEY3 = 0xFFFF;
    CsmRegs.KEY4 = 0xFFFF;
    CsmRegs.KEY5 = 0xFFFF;
    CsmRegs.KEY6 = 0xFFFF;
    CsmRegs.KEY7 = 0xFFFF;
    EDIS;

    //
    // Perform a dummy read of the password locations if they match the key 
    // values, the CSM will unlock
    //
    temp = CsmPwl.PSWD0;
    temp = CsmPwl.PSWD1;
    temp = CsmPwl.PSWD2;
    temp = CsmPwl.PSWD3;
    temp = CsmPwl.PSWD4;
    temp = CsmPwl.PSWD5;
    temp = CsmPwl.PSWD6;
    temp = CsmPwl.PSWD7;

    //
    // If the CSM unlocked, return succes, otherwise return failure.
    //
    if (CsmRegs.CSMSCR.bit.SECURE == 0)
    {
        return STATUS_SUCCESS;
    }
    else 
    {
        return STATUS_FAIL;
    }
}

Best,

Matthew