zero_out_integrity_word function is used to clear the specified location of checksum. A lockup can occur when the zero_out_integrity_word function does not compile in 32-bit mode. This function is normally in an independent file named zero_out_integrity_word.c. The function name or file name can be slightly different from project to project, but generally looks like the following.

#define program_flash_integrity_word (*((volatile unsigned long *) 0x7ffc))
//last word in flash, when executing from Flash.  used to store integrity code

void zero_out_integrity_word(void)
{
    DecRegs.FLASHILOCK.all = 0x42DC157E;// Write key to Program Flash Interlock Register
    DecRegs.MFBALR1.all = MFBALRX_BYTE0_BLOCK_SIZE_32K; //enable program flash write    program_flash_integrity_word = 0;
   DecRegs.MFBALR1.all = MFBALRX_BYTE0_BLOCK_SIZE_32K + MFBALRX_BYTE0_RONLY;

    while(DecRegs.PFLASHCTRL.bit.BUSY != 0)
    {
        ; //do nothing while it programs
}

    return;
}

To check whether this function/file is compiled in 32-bit mode:

• Right click on zero_out_integrity_word.c > Properties > CCS Build > ARM Compiler > Processor Option > Designate code state.
• If currently 16, change to 32 (as shown in Figure 2-2.)
• Rebuild the project.

Note that this option is done with the configuration in CCS, so the zero_out_integrity_word function can possibly fail when the CCS version or compiler version is changed.

Another option is to use a preprocessor directive #pragma telling the compiler to compile the specified function in 32-bit mode. The following is an example.

#define program_flash_integrity_word (*((volatile unsigned long *) 0x7ffc))
//last word in flash, when executing from Flash.  used to store integrity code

#pragma CODE_STATE(zero_out_integrity_word, 32) // 16 = thumb mode, 32 = ARM mode
void zero_out_integrity_word(void)
{
    DecRegs.FLASHILOCK.all = 0x42DC157E;// Write key to Program Flash Interlock Register
    DecRegs.MFBALR1.all = MFBALRX_BYTE0_BLOCK_SIZE_32K; //enable program flash write
    program_flash_integrity_word = 0;
   DecRegs.MFBALR1.all = MFBALRX_BYTE0_BLOCK_SIZE_32K + MFBALRX_BYTE0_RONLY; 
    while(DecRegs.PFLASHCTRL.bit.BUSY != 0)
    {
        ; //do nothing while it programs
}

    return;
}