Flash programming error

Hello,

​

I am verifying my flash write program.

The first writing is ok, but the error occurred from the second writing.

The following is my flash write program.

int cmd_flash_write(void) 
{
	uint32_t s_addr;
	uint32_t data[512];
	uint32_t len, i, status;
 
	s_addr = atoi(argv[1]);
	len = atoi(argv[2]);
 
	/* Random data */
	for(i = 0; i < len; i++) {
		data[i] = rand() % 0xffffffff;
	}
 
	FLASH_Unlock(); 
	status = FLASH_If_Write(&s_addr, (U32*)&data[0] ,len);
	FLASH_Lock();
 
	Uart_Printf("status : %d\n", status);
	
	return TRUE;
}

U32 FLASH_If_Write(__IO U32* FlashAddress, U32* Data ,U16 DataLength){
	U32 i = 0;
	U32 a, b;
 
	//dbg_printf("FlashAddress : 0x%.8x 0x%.8x %d\n", *FlashAddress, *Data, DataLength);
	for (i = 0; (i < DataLength) && (*FlashAddress <= (USER_FLASH_END_ADDRESS-4)); i++){
		if((*FlashAddress>=BOOTLOADER_START_ADDRESS) && (*FlashAddress<=BOOTLOADER_END_ADDRESS)) { //protect the boot area
			dbg_printf("ADDRESS : 0x%.8x Error\n", *FlashAddress);
			return (1);
		}
		
		/* Device voltage range supposed to be [2.7V to 3.6V], the operation will
		be done by word */ 
		if (FLASH_ProgramWord(*FlashAddress, *(U32*)(Data+i)) == FLASH_COMPLETE){
			a = *(__IO U32*)*FlashAddress;
			b = *(U32*)(Data+i);
 
			/* Check the written value */
			if (a != b){
				/* Flash content doesn't match SRAM content */
				return(2);
			}
 
			/* Increment FLASH destination address */
			*FlashAddress += 4;
		}
		else{
			/* Error occurred while writing data in Flash memory */
			return (1);
		}
	}
 
	return (0);
}

The return value of the FLASH_If_Write() function is '2'.

It means that the written data is different from the read data.

Why does this difference occur from the second time?

Thanks