PIC18F2450/4450
EXAMPLE 6-3:
WRITING TO FLASH PROGRAM MEMORY
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
D'64’
COUNTER
BUFFER_ADDR_HIGH
FSR0H
BUFFER_ADDR_LOW
FSR0L
CODE_ADDR_UPPER
TBLPTRU
CODE_ADDR_HIGH
TBLPTRH
CODE_ADDR_LOW
TBLPTRL
; number of bytes in erase block
; point to buffer
; Load TBLPTR with the base
; address of the memory block
READ_BLOCK
TBLRD*+
MOVF
MOVWF
; read into TABLAT, and inc
; get data
; store data
; done?
TABLAT, W
POSTINC0
DECFSZ COUNTER
BRA
READ_BLOCK
; repeat
MODIFY_WORD
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
DATA_ADDR_HIGH
FSR0H
DATA_ADDR_LOW
FSR0L
NEW_DATA_LOW
POSTINC0
NEW_DATA_HIGH
INDF0
; point to buffer
; update buffer word
ERASE_BLOCK
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
BCF
BSF
BSF
BCF
CODE_ADDR_UPPER
TBLPTRU
CODE_ADDR_HIGH
TBLPTRH
CODE_ADDR_LOW
TBLPTRL
EECON1, CFGS
EECON1, WREN
EECON1, FREE
INTCON, GIE
; load TBLPTR with the base
; address of the memory block
; access Flash program memory
; enable write to memory
; enable Row Erase operation
; disable interrupts
MOVLW
MOVWF
MOVLW
MOVWF
BSF
55h
EECON2
0AAh
EECON2
EECON1, WR
INTCON, GIE
Required
Sequence
; write 55h
; write 0AAh
; start erase (CPU stall)
; re-enable interrupts
; dummy read decrement
; point to buffer
BSF
TBLRD*-
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
BUFFER_ADDR_HIGH
FSR0H
BUFFER_ADDR_LOW
FSR0L
D’4’
COUNTER1
WRITE_BUFFER_BACK
MOVLW
D’16’
; number of bytes in holding register
MOVWF
WRITE_BYTE_TO_HREGS
MOVF
COUNTER
POSTINC0, W
TABLAT
; get low byte of buffer data
; present data to table latch
; write data, perform a short write
; to internal TBLWT holding register.
; loop until buffers are full
MOVWF
TBLWT+*
DECFSZ COUNTER
BRA WRITE_WORD_TO_HREGS
DS39760A-page 80
Advance Information
© 2006 Microchip Technology Inc.
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