Problem in Reading from Flash Memory Location

Priyanka Dhomne

unsigned long Flash_ptr_start = 0X10000;  

Priyanka Dhomne

        // unsigned long *Flash_ptr_start = BUF;

You have two different definitions of Flash_ptr_start.

The global one is a long int variable, the one define din the function is a pointer variable that points to a long int value.

If you use the pointer definition inside your funciton, it will shadow the global long int variable (don't ou get a compiler warning about this?).

You're going through some implicit typecasting here.

unsigned long *Flash_ptr_start = BUF;        

This assignment is commented in code...........i had not used in this code.only global one is used.

Priyanka Dhomne

This assignment is commented in code...........i had not used in this code.only global one is used.

I interpreted the comment behind this line and your initial description that it works with one and not with the other (e.g. one version has it commented, the other one not).

If you give an either/or description of the problem ("If I..." implies that it works if you don't), you should also give the two different code versions. I assumed that this comment was the difference.

k.......... i tell you what whole problem is .

In code when we intialize  unsigned long *Flash_ptr = BUF; (it will point to first mem location  0x10000 ), Writing into Flash is Proper ,while Reading from Flash it will not into loop itself ?

unsigned long BUF[ ] = {0X10000,0X20000};

unsigned long *Flash_ptr = BUF;

unsigned long Flash_ptr_start = 0X10000;  

/**** write value into flash Memory****/

void flash_write_val()
{ 
char temp[5];

while (FCTL3 & BUSY);                                      // Check if Flash being used
FCTL3 = FWKEY; 
FCTL1 = FWKEY+BLKWRT;                               // Enable long-word write

(*(unsigned long *)Flash_ptr) = rec_long;        // Write to Flash

check = (*(unsigned long *)Flash_ptr); 

temp[0] = check ; //LSB
temp[1] = (check >> 8) ;
temp[2] = (check >> 16);
temp[3] = (check >> 24);
temp[4] = '\0';

halLcdPrintLine("valwrt2flash..",4,OVERWRITE_TEXT);          // Here we get Value which is Written into Flash Mem Location
halLcdPrintLine(temp,5,OVERWRITE_TEXT);

Flash_ptr++;                                                                                    // Increment Flash mem location to read val frm next location
while (FCTL3 & BUSY );                                                                 // Check if Flash being used
FCTL1 = FWKEY;                                                                             // Clear WRT bit
FCTL3 = FWKEY+LOCK;                                                                // Set LOCK bit
}

/****Read  value from flash Memory****/

void flash_read_val()
{ 
         char temp[5];

          // unsigned long *Flash_ptr_start = BUF;                          // if i set flash_ptr_start value equal to directly buffer it will not go into the loop why ??
         unsigned long Flash_end = 0X10001;

         while( Flash_ptr_start < 0X10001 )
       {
             P1OUT |= LED2;
            Flash_data = 0;
            Flash_data = *(unsigned long *)Flash_ptr_start;

             P1OUT &= ~LED2;

               temp[0] = Flash_data ; //LSB
               temp[1] = (Flash_data >> 8) ;
               temp[2] = (Flash_data >> 16);
                temp[3] = (Flash_data >> 24);
                 temp[4] = '\0';

            halLcdPrintLine("valrd frm flash..",6,OVERWRITE_TEXT);          // while reading from same memory location i get result zero why ????
            halLcdPrintLine(temp,7,OVERWRITE_TEXT);
             Flash_ptr_start++; 

           delay(500);
    }
}

 This code is not worked thats why i tried and   initalize   unsigned long *Flash_ptr = 0X10000(Directly pointing to memory location);  In this Case it will go into the loop but give output zero.

Is problem in this code wrt  pointer increment ,while incrementing it is not pointing to another location(0X10001),I Hope you Understand my Problem ,Thank You 

Okay, I see some oddities...

1) the loop is controlled by Flash_ptr_start, so it makes no difference where Flash_ptr points to.

2) I'm not sure whether your constants are right. Ic you write 0x10000, this is an int, not a long int, and migh tbe truncated to 0x0000 by the parser before it is assigned. Try using 0x10000L instead. I'm not sure what the C standard and teh compiler docu tells about long integer constants, but IIRC, some past problems in this forum were solved by adding the long modifier to the constant.
If this is the case, then 0x10000 truncates to 0x0000, which is smaller than (0x10001 truncated to) 0x0001 in the if. However, BUF is > 0x0001 and won't enter the loop.

3) (usigned long *)Flash_ptr_start may result in a 16 bit pointer if you don't use large data model. In small data model (the default), data pointers are 16 bit only, so the cast truncates the value of Flash_ptr_start and you're reading from address 0x00000 instead of 0x10000.

2) I'm not sure whether your constants are right. Ic you write 0x10000, this is an int, not a long int, and migh tbe truncated to 0x0000 by the parser before it is assigned. Try using 0x10000L instead. I'm not sure what the C standard and teh compiler docu tells about long integer constants, but IIRC, some past problems in this forum were solved by adding the long modifier to the constant.
If this is the case, then 0x10000 truncates to 0x0000, which is smaller than (0x10001 truncated to) 0x0001 in the if. However, BUF is > 0x0001 and won't enter the loop

I Tried to run my Code using 0x10000L ,Still not going  into the Loop.I understand that what you are trying to tell me that pointer is points not pointing to 0x10000 ,but it will point to 0x0000 .

Do you have any code Examples  Regarding Flash Read  Write,Which would help me for reading and writing large amount of data from flash.

Priyanka Dhomne

Do you have any code Examples  Regarding Flash Read  Write,Which would help me for reading and writing large amount of data from flash.

Sorry, my flash writing code is hand-crafted assembly for MSPGCC.

However, I suggest starting writing to the info memory area below 64k first. If this works, you can go and extend the code for >64k memory.