Datasheet

PIC24FJ256DA210 FAMILY
DS39969B-page 86  2010 Microchip Technology Inc.
5.6.2 PROGRAMMING A SINGLE WORD
OF FLASH PROGRAM MEMORY
If a Flash location has been erased, it can be pro-
grammed using table write instructions to write an
instruction word (24-bit) into the write latch. The
TBLPAG register is loaded with the 8 Most Significant
Bytes (MSB) of the Flash address. The TBLWTL and
TBLWTH instructions write the desired data into the
write latches and specify the lower 16 bits of the pro-
gram memory address to write to. To configure the
NVMCON register for a word write, set the NVMOP bits
(NVMCON<3:0>) to ‘0011’. The write is performed by
executing the unlock sequence and setting the WR bit
(see Example 5-5). An equivalent procedure in ‘C’
compiler, using the MPLAB C30 compiler and built-in
hardware functions is shown in Example 5-6.
EXAMPLE 5-5: PROGRAMMING A SINGLE WORD OF FLASH PROGRAM MEMORY
EXAMPLE 5-6: PROGRAMMING A SINGLE WORD OF FLASH PROGRAM MEMORY
(‘C’ LANGUAGE CODE)
; Setup a pointer to data Program Memory
MOV #tblpage(PROG_ADDR), W0 ;
MOV W0, TBLPAG ;Initialize PM Page Boundary SFR
MOV #tbloffset(PROG_ADDR), W0 ;Initialize a register with program memory address
MOV #LOW_WORD_N, W2 ;
MOV #HIGH_BYTE_N, W3 ;
TBLWTL W2, [W0] ; Write PM low word into program latch
TBLWTH W3, [W0++] ; Write PM high byte into program latch
; Setup NVMCON for programming one word to data Program Memory
MOV #0x4003, W0 ;
MOV W0, NVMCON ; Set NVMOP bits to 0011
DISI #5 ; Disable interrupts while the KEY sequence is written
MOV.B #0x55, W0 ; Write the key sequence
MOV W0, NVMKEY
MOV.B #0xAA, W0
MOV W0, NVMKEY
BSET NVMCON, #WR ; Start the write cycle
NOP ; Required delays
NOP
// C example using MPLAB C30
unsigned int offset;
unsigned long progAddr = 0xXXXXXX; // Address of word to program
unsigned int progDataL = 0xXXXX; // Data to program lower word
unsigned char progDataH = 0xXX; // Data to program upper byte
//Set up NVMCON for word programming
NVMCON = 0x4003; // Initialize NVMCON
//Set up pointer to the first memory location to be written
TBLPAG = progAddr>>16; // Initialize PM Page Boundary SFR
offset = progAddr & 0xFFFF; // Initialize lower word of address
//Perform TBLWT instructions to write latches
__builtin_tblwtl(offset, progDataL); // Write to address low word
__builtin_tblwth(offset, progDataH); // Write to upper byte
asm(“DISI #5”); // Block interrupts with priority <7
// for next 5 instructions
__builtin_write_NVM(); // C30 function to perform unlock
// sequence and set WR