24.14 Row Programming

The largest block of data that can be programmed is a row.

Unlike Word and Quad Word Programming where the data source is stored in SFR memory, Row programming source data is stored in SRAM. The NVMSRCADDR register is a pointer to the physical location of the source data for Row programming.

Like other Non-Volatile Memory (NVM) programming commands, the NVMADDR register points to the target address of the operation. Row programming always occurs on row boundaries with the row size of 1024, bits 0 through 9 of the NVMADDR register are ignored.

Row Word programming will only succeed if the target address is in a page that is not write-protected. When a row is programmed, it must be erased before any Word in it can be programmed again, even if changing a bit from an erased ‘1’ state to a ‘0’ state.

Array rowbuff is populated with data and programmed into a row located at physical address 0x1008000.

Note: When assigning the value to the NVMSRCADDR register, it must be converted to a physical address.

Row Programming Code Example:

…

unsigned long rowbuff[256]; // example is for a 256 Word row size. 
int x;                         // loop counter

// put some data in the source buffer
      for (x = 0; x < (sizeof(rowbuff) * sizeof (int)); x++)
            ((char *)rowbuff)[x] = x;

// set destination row address
     NVMADDR = 0x1008000;             // row physical address

// set source address. Must be converted to a physical address.
     NVMSRCADDR = (unsigned int)((int)rowbuff & 0x1FFFFFF);

// define Flash operation
      NVMCONbits.NVMOP = 0x3;            // NVMOP for Row programming

// Enable Flash Write
      NVMCONbits.WREN = 1;

// commence programming
      NVMInitiateOperation();            // see Initiate NVM Operation (Unlock Sequence Example)

// Wait for WR bit to clear
      while(NVMCONbits.WR);

// Disable future Flash Write/Erase operations
       NVMCONbits.WREN = 0;

// Check Error Status
       if(NVMCON & 0x3000)            // mask for WRERR and LVDERR bits
      { 
         // process errors
       }
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