MSP430FR5969: Forgets program or program is corrupted

I read over SLAA628 - FRAM Best Practices. Wow, this was very helpful. I was not using MPU. It's crazy to think that I have done so much with FRAM MSP430's and didn't even know about MPU.

That said, I'd like to help out anyone who may be interested.

However, I am running at 8 MHz in active mode:

void initClk()
{
    CSCTL0_H = 0xA5;
    CSCTL0_L = 0;
    CSCTL1 = DCORSEL + DCOFSEL1 + DCOFSEL0;     /* Set DCO setting = 8MHz*/
    CSCTL2 = SELA_1 + SELS_3 + SELM_3;          /*set ACLK - VLO, the rest = MCLK = DCO*/
    CSCTL3 = DIVA__16 + DIVS_0 + DIVM_0;		/* set clock dividers to 0. Set ACLK/16*/

    /* Globally enable interrupts */
    __bis_SR_register(GIE);
}

2. Memory Layout Partitioning. I'm well familiar with command files from my work with C2000 chips, and I had a very old cmd file: Version 1.127. When I changed my device in properties and had CCS create a new cmd file, it produced Version 1.207. I didn't realize that I likely need that right away so before that, I moved on with the FRAM Best Practices doc.

3. I compared my cmd file using DiffMerge to C:\ti\CC3100SDK_1.2.0\cc3100-sdk\platform\msp430fr5969lp\example_project_ccs\getting_started_with_wlan_station\lnk_msp430fr5969.cmd and the only difference was that I had added two lines between .stack and .infoA:

	.TI.noinit 		: {} > FRAM 			/* For #pragma NOINIT */
	.TI.persistent 	: {} > FRAM 			/* For #pragma PERSISTENT */

I recall that I got these lines from some e2e post to solve a problem I was having with variables being reset on power cycle. That was a long time ago.

IS IT POOR PRACTICE TO PUT A POINTER TO A FUNCTION IN PERSISTENT? I have this warning as a result: #10229-D null: output section ".data" refers to load symbol "initFunction" and hence cannot be compressed; compression "lzss" is ignored

I enabled MPU using the MPU Wizard and I got these errors:

undefined first referenced
symbol in file
--------- ----------------
MPUSEG C:\ti\ccs910\ccs\tools\compiler\ti-cgt-msp430_18.12.2.LTS\lib\rts430x_lc_rd_eabi.lib<mpu_init.c.obj>
__mpusam C:\ti\ccs910\ccs\tools\compiler\ti-cgt-msp430_18.12.2.LTS\lib\rts430x_lc_rd_eabi.lib<mpu_init.c.obj>
__mpuseg C:\ti\ccs910\ccs\tools\compiler\ti-cgt-msp430_18.12.2.LTS\lib\rts430x_lc_rd_eabi.lib<mpu_init.c.obj>

I solved that by Project >> Add Files: C:\ti\ccs910\ccs\ccs_base\msp430\lib\FR59xx\MSPMPU_INIT_LIB_CCS_msp430_large_code_restricted_data.lib
aka
${CCS_BASE_ROOT}\msp430\lib\FR59xx\MSPMPU_INIT_LIB_CCS_msp430_large_code_restricted_data.lib

When I ran my code I couldn't write to my PERSISTENT memory anymore.

I found that my linker file didn't have persistent in the right spot when I compared it to a freshly generated cmd file. So, I started using the freshly CCS generated cmd file. The new file has this:

SECTIONS
{
    GROUP(RW_IPE)
    {
        GROUP(READ_WRITE_MEMORY)
        {
           .TI.persistent : {}              /* For #pragma persistent            */
           .cio           : {}              /* C I/O Buffer                      */
           .sysmem        : {}              /* Dynamic memory allocation area    */
        } PALIGN(0x0400), RUN_START(fram_rw_start)

So then I got errors that the program wouldn't fit in memory for .data and .stack. However, my old cmd file had .data and .stack in RAM just like the new file, but I had .bss in FRAM and not RAM.

But, when I changed .bss to FRAM, the program just wouldn't work. What I learned was that now that I am using the MPU I just can't assign sections of code to FRAM because it is protected by the MPU. I had a few global string variables that were just too long. They had to be put in FRAM so I #pragma PERSISTENT(...) those variables and voila, my code worked again.

Now, I have to cross my fingers that I can figure out what part of the code was causing the FRAM write to program memory. 

IS THERE ANY OTHER CODE I NEED SO THAT I WILL GET A PUC IF THIS ERROR OCCURS?

For instance, is it recommended to now have some of this code that I found in msp430fr59xx_mpu_02.c or did the MPU Wizard handle this?

  WDTCTL = WDTPW | WDTHOLD;                 // Stop WDT

  // Configure GPIO
  P1DIR |= BIT0;                            // Configure P1.0 for LED

  // Disable the GPIO power-on default high-impedance mode to activate
  // previously configured port settings
  PM5CTL0 &= ~LOCKLPM5;

  while (MPUCTL1 & MPUSEG2IFG)              // has reset occurred due to Seg2
  {
    P1OUT ^= BIT0;                          // Toggle LED
    __delay_cycles(30000);                  // Delay to see toggle
  }

  // Configure MPU
  MPUCTL0 = MPUPW;                          // Write PWD to access MPU registers
  MPUSEGB1 = 0x0600;                        // B1 = 0x6000; B2 = 0x8000
  MPUSEGB2 = 0x0800;                        // Borders are assigned to segments
  
  //  Segment 1 - Execute, Read
  //  Segment 2 - Violation, Execute, Read
  //  Segment 3 - Execute, Read
  MPUSAM =             MPUSEG1RE | MPUSEG1XE |
           MPUSEG2VS | MPUSEG2RE | MPUSEG2XE |
                       MPUSEG3RE | MPUSEG3XE |
                       MPUSEGIRE | MPUSEGIXE | MPUSEGIWE;
  MPUCTL0 = MPUPW | MPUENA;               // Enable MPU protection

  Data = 0x88;

  // Cause an MPU violation by writing to segment 2
  ptr = (unsigned int  *)0x6002;
  *ptr = Data;

  while(1);                                 // Code never gets here

OTHER NOTES:

There appears to be a typo in section 6.3.1:
sytem_pre_init.c should be system_pre_init.c?