CCS/MSP430FR2422: Checksum of program code

#include <msp430.h> 
#include <stdint.h>

/*
 * Notes: By default both data and program FRAM memory is enabled and must be
 * disabled in order to write to these sections.
 * For more information on this topic see section 5.12.22
 * https://www.ti.com/lit/ug/slau132v/slau132v.pdf
 *
 * Noinit and persistent variables behave identically with the exception of
 * whether or not they are initialized at load time.
 * The NOINIT pragma may be used only with uninitialized variables. It
 * prevents such variables from being set to 0 during a reset.
 * It may be used in conjunction with the LOCATION pragma to map variables
 * to special memory locations, like memory-mapped registers, without
 * generating unwanted writes.
 * The PERSISTENT pragma may be used only with statically-initialized variables.
 * It prevents such variables from being initialized during a reset.
 * Persistent variables disable startup initialization; they are given an
 * initial value when the code is loaded, but are never again initialized.
 * By default, noinit or persistent variables are placed in sections
 * named .TI.noinit and .TI.persistent, respectively. The location of these
 * sections is controlled by the linker command file. Typically .TI.persistent
 * sections are placed in FRAM for devices that support FRAM and .TI.noinit sections
 * are placed in RAM.
 */
/*
 * Some easy to use #defines
 */
#define DISABLE_PF_WRITE_PROTECT        SYSCFG0 = FRWPPW | DFWP
#define DISABLE_DF_WRITE_PROTECT        SYSCFG0 = FRWPPW | PFWP
#define DISABLE_PF_DF_WRITE_PROTECT     SYSCFG0 = FRWPPW
#define DISABLE_ALL_WRITE_PROTECT       SYSCFG0 = FRWPPW

#define ENABLE_PF_WRITE_PROTECT         SYSCFG0 = FRWPPW | PFWP
#define ENABLE_DF_WRITE_PROTECT         SYSCFG0 = FRWPPW | DFWP
#define ENABLE_PF_DF_WRITE_PROTECT      SYSCFG0 = FRWPPW | PFWP | DFWP
#define ENABLE_ALL_WRITE_PROTECT        SYSCFG0 = FRWPPW | PFWP | DFWP

/*
 * Example
 * Declare variable 'peanut' persistent in Info memory at location 0x1800.
 * (initialize only once at load time = 0)
 *
 */
#pragma PERSISTENT(peanut)
#pragma LOCATION(peanut, 0x1800)
uint16_t peanut = 0;

/*
 * Example
 * Declare variable 'peach' persistent in Program memory at location 0xE000.
 * (initialize only once at load time = 0x1234)
 *
 */
#pragma PERSISTENT(peach)
#pragma LOCATION(peach, 0xE002)
uint16_t peach = 0x1234;


/*
 * Example
 * Declare variable 'apple, compiler will place automatically
 * (initialize only once at load time = 0x55AA)
 */
#pragma PERSISTENT(apple)
uint16_t apple = 0x55AA;

/*
 * Example
 * Declare variable 'walnut' noinit in Info memory at location 0x1802.
 * (is not initialized at reset)
 *
 */
#pragma NOINIT(walnut)
#pragma LOCATION(walnut, 0x1802)
uint16_t walnut;

uint16_t SYSCFG0_copy;

int main(void)
{
	WDTCTL = WDTPW | WDTHOLD;	// stop watchdog timer

	SYSCFG0_copy = SYSCFG0 & (PFWP | DFWP);     // let's first confirm FRAM protection is on by default

	peanut = 1;                                 // won't work because DFWP is enabled by default

	DISABLE_DF_WRITE_PROTECT;

	peanut = 1;                                 // this time it worked

	walnut = 2;                                 // verify we can change walnut

	apple = 0x55AA;                             // won't work because PFWP is enabled by default

	DISABLE_PF_WRITE_PROTECT;

	apple = 0xAA55;                            // this time it worked
	
	peach = 0;                                 // verify we can change peach

	DISABLE_ALL_WRITE_PROTECT;                 // Don't forget to protect when done.

	while(1);

}