Microchip Technology MA180025 データシート
PIC18F87J90 FAMILY
DS39933D-page 96
2010 Microchip Technology Inc.
EXAMPLE 7-3:
WRITING TO FLASH PROGRAM MEMORY
MOVLW
CODE_ADDR_UPPER
; Load TBLPTR with the base address
MOVWF
TBLPTRU
; of the memory block, minus 1
MOVLW
CODE_ADDR_HIGH
MOVWF
TBLPTRH
MOVLW
CODE_ADDR_LOW
MOVWF
TBLPTRL
ERASE_BLOCK
BSF
EECON1, WREN
; enable write to memory
BSF
EECON1, FREE
; enable Erase operation
BCF
INTCON, GIE
; disable interrupts
MOVLW
55h
MOVWF
EECON2
; write 55h
MOVLW
0AAh
MOVWF
EECON2
; write 0AAh
BSF
EECON1, WR
; start erase (CPU stall)
BSF
INTCON, GIE
; re-enable interrupts
MOVLW
D'16'
MOVWF
WRITE_COUNTER
; Need to write 16 blocks of 64 to write
; one erase block of 1024
RESTART_BUFFER
MOVLW
D'64'
MOVWF
COUNTER
MOVLW
BUFFER_ADDR_HIGH
; point to buffer
MOVWF
FSR0H
MOVLW
BUFFER_ADDR_LOW
MOVWF
FSR0L
FILL_BUFFER
...
; read the new data from I2C, SPI,
; USART, etc.
WRITE_BUFFER
MOVLW
D’64
; number of bytes in holding register
MOVWF
COUNTER
WRITE_BYTE_TO_HREGS
MOVFF
POSTINC0, WREG
; 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_BYTE_TO_HREGS
PROGRAM_MEMORY
BSF
EECON1, WREN
; enable write to memory
BCF
INTCON, GIE
; disable interrupts
MOVLW
55h
Required
MOVWF
EECON2
; write 55h
Sequence
MOVLW
0AAh
MOVWF
EECON2
; write 0AAh
BSF
EECON1, WR
; start program (CPU stall)
BSF
INTCON, GIE
; re-enable interrupts
BCF
EECON1, WREN
; disable write to memory
DECFSZ
WRITE_COUNTER
; done with one write cycle
BRA
RESTART_BUFFER
; if not done replacing the erase block