Accessing to SRAM on MSP430FR5969

Hi

I am measuring the accessing time for SRAM on MSP430FR5969. According to the datasheet, the address is from 001C00h-0023FFh. So I use this code to write to SRAM.

#define OUTPIN BIT5

/*
 * main.c
 */
void SRAM_write(void);
unsigned int data=0x11;

#define SRAM_TEST_START 0x1D00

int main(void) {
	int i=5;
    WDTCTL = WDTPW | WDTHOLD;	// Stop watchdog timer
    P1OUT &= ~OUTPIN;
    P1DIR |= OUTPIN;
    PM5CTL0 &= ~LOCKLPM5;
    while(1)
    {
    	for (i=0;i<200;i++)
    		SRAM_write();
    	P1OUT ^= OUTPIN;
    }
}

void SRAM_write(void)
{
	int i;
	SRAM_ptr_write = (unsigned int *)SRAM_TEST_START;
	for(i=0;i<256;i++)
	{
		*SRAM_ptr_write=data;
		SRAM_ptr_write++;
	}
	
}

But the accessing time (when measuring, it's the time writing to ram 256*200 times)  is equal to the FRAM, which means I am accessing to the FRAM.

Then I use the following code, using a vector instead of the pointer. And the time is 3/4 of previous time.

#define OUTPIN BIT5

/*
 * main.c
 */
void SRAM_write(void);
unsigned int data=0x11;

#pragma DATA_SECTION(SRAM_ptr_write, ".sram")
volatile unsigned int SRAM_ptr_write[257];

int main(void) {
	int i=5;
    WDTCTL = WDTPW | WDTHOLD;	// Stop watchdog timer
    P1OUT &= ~OUTPIN;
    P1DIR |= OUTPIN;
    PM5CTL0 &= ~LOCKLPM5;
    while(1)
    {
    	//P1OUT ^= OUTPIN;
    	for (i=0;i<200;i++)
    		SRAM_write();
    	P1OUT ^= OUTPIN;
    }
}

void SRAM_write(void)
{
	int i;
	for(i=0;i<256;i++)
	{
		SRAM_ptr_write[i]=data;
	}
	
}

So what's the problem with my first code? Why can't I access to the SRAM using the pointer?

Thanks!

Yin