64GA110 datasheet(63/330 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS39905E-page 63

PIC24FJ256GA110 FAMILY

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 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 program 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, as shown in

Example 5-7. An equivalent procedure in C, using the

MPLAB C30 compiler and built-in hardware functions,

is shown in Example 5-8.

EXAMPLE 5-7:

PROGRAMMING A SINGLE WORD OF FLASH PROGRAM MEMORY

(ASSEMBLY LANGUAGE CODE)

EXAMPLE 5-8:

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, W2

;

MOV

#HIGH_BYTE, 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

; Disable interrupts while the KEY sequence is written

MOV

#0x55, W0

; Write the key sequence

MOV

W0, NVMKEY

MOV

#0xAA, W0

MOV

W0, NVMKEY

BSET

NVMCON, #WR

; Start the write cycle

NOP

; Insert two NOPs after the erase

NOP

; Command is asserted

// 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

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