Datasheet

PIC18FXX2
DS39564C-page 62 © 2006 Microchip Technology Inc.
EXAMPLE 5-3: WRITING TO FLASH PROGRAM MEMORY
MOVLW D'64 ; number of bytes in erase block
MOVWF COUNTER
MOVLW BUFFER_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW BUFFER_ADDR_LOW
MOVWF FSR0L
MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
READ_BLOCK
TBLRD*+ ; read into TABLAT, and inc
MOVF TABLAT, W ; get data
MOVWF POSTINC0 ; store data
DECFSZ COUNTER ; done?
BRA READ_BLOCK ; repeat
MODIFY_WORD
MOVLW DATA_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW DATA_ADDR_LOW
MOVWF FSR0L
MOVLW NEW_DATA_LOW ; update buffer word
MOVWF POSTINC0
MOVLW NEW_DATA_HIGH
MOVWF INDF0
ERASE_BLOCK
MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
BSF EECON1,EEPGD ; point to FLASH program memory
BCF EECON1,CFGS ; access FLASH program memory
BSF EECON1,WREN ; enable write to memory
BSF EECON1,FREE ; enable Row Erase operation
BCF INTCON,GIE ; disable interrupts
MOVLW 55h
MOVWF EECON2 ; write 55h
MOVLW AAh
MOVWF EECON2 ; write AAh
BSF EECON1,WR ; start erase (CPU stall)
BSF INTCON,GIE ; re-enable interrupts
TBLRD*- ; dummy read decrement
WRITE_BUFFER_BACK
MOVLW 8 ; number of write buffer groups of 8 bytes
MOVWF COUNTER_HI
MOVLW BUFFER_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW BUFFER_ADDR_LOW
MOVWF FSR0L
PROGRAM_LOOP
MOVLW 8 ; number of bytes in holding register
MOVWF COUNTER
WRITE_WORD_TO_HREGS
MOVF POSTINC0, W ; get low byte of buffer data
MOVWF TABLAT ; present data to table latch
TBLWT+* ; write data, perform a short write
; to internal TBLWT holding register.
DECFSZ COUNTER ; loop until buffers are full
BRA WRITE_WORD_TO_HREGS