How to access the flash outside the 64K of the MSP430F5438 microcontroller

2. In the Target page, Data Model option, select Medium or Large in 4.
3. Explanation:
- Select SMALL to access only the space within 64K, and the space outside can only be accessed by internal functions
- Select Medium to access the space within 1M
- Select Large to access the entire space

1. F5XX 430X 
2. Select Large small medium. The effect is to change the number of bytes occupied by the pointer variable. The default pointer variable in IAR is 2 bytes. Select large to occupy 4 bytes, so the pointer can access addresses beyond the 64K range.
3. You can use IAR internal functions, */

void __data20_write_char (unsigned long __addr,
unsigned char __value);

void __data20_write_short(unsigned long __addr,
unsigned short __value);

void __data20_write_long (unsigned long __addr,
unsigned long __value);

unsigned char __data20_read_char (unsigned long __addr);
unsigned long __data20_read_long (unsigned long __addr);

How to operate the flash memory of 5438
I would like to ask about the flash memory operation of MSP430F5438. The code is shown below. Why does the fixed address of the flash memory not change?

Code:
void main(void)
{
 

  unsigned long SEGMENT = 0x20000ul;

  WriteFlash(SEGMENT);
  FlashErase(SEGMENT);

  while(1)；

   
}Code:
//Erase Flash address: adr specifies address Y
void FlashErase(unsigned long pAddr)
{
  
  uchar * Flash_ptr = (uchar *)pAddr;                 
  
  _DINT();                                  
                                            
  while(BUSY & FCTL3);
  FCTL3 = FWKEY;                            
  FCTL1 = FWKEY+ERASE;                     
  *Flash_ptr = 0;                           
  while(BUSY & FCTL3);
  FCTL3 = FWKEY+LOCK;                       
  _EINT();
}Code:
//Write Flash address: adr specifies address,
void WriteFlash(unsigned long pAddr)
{
  _DINT();
  unsigned int i;
  uchar * Flash_ptr = (uchar *)pAddr;       
  while (FCTL3&BUSY);
  FCTL3 = FWKEY;                         
  FCTL1 = FWKEY+WRT;                       
  for(i = 0; i < 128; i++)
  {
    *(Flash_ptr++) = record1[i]; 
    while(!(WAIT & FCTL3));                 
  }
  while (FCTL3&BUSY);
  FCTL1 = FWKEY;                           
  FCTL3 = FWKEY+LOCK;                                        
  _EINT();
}