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DS39996F-page 88

 2010-2011 Microchip Technology Inc.

6.6.2

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 (MSBs) 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 

). An equivalent procedure in ‘C’

compiler, using the MPLAB C30 compiler and built-in
hardware functions, is shown in 

; 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