PIC24FJ64GA datasheet(48/262 Pages) MICROCHIP

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PIC24FJ64GA004 FAMILY

DS39881C-page 46

Preliminary

4.6.2

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 (see

Example 4-4).

EXAMPLE 4-4:

PROGRAMMING A SINGLE WORD OF FLASH PROGRAM MEMORY

; 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

; 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

; 2 NOPs required after setting WR

NOP

;

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