Datasheet

© 2009 Microchip Technology Inc. DS39775C-page 105
PIC18F87J50 FAMILY
6.5.2 FLASH PROGRAM MEMORY WRITE
SEQUENCE (WORD PRORAMMING).
The PIC18F87J10 family of devices have a feature that
allows programming a single word (two bytes). This
feature is enabled when the WPROG bit is set. If the
memory location is already erased, the following
sequence is required to enable this feature:
1. Load the Table Pointer register with the address
of the data to be written. (It must be an even
address.)
2. Write the 2 bytes into the holding registers by
performing table writes. (Do not post-increment
on the second table write.)
3. Set the WREN bit (EECON1<2>) to enable
writes and the WPROG bit (EECON1<5>) to
select Word Write mode.
4. Disable interrupts.
5. Write 55h to EECON2.
6. Write AAh to EECON2.
7. Set the WR bit. This will begin the write cycle.
8. The CPU will stall for duration of the write for TIW
(see parameter D133A).
9. Re-enable interrupts.
EXAMPLE 6-4: SINGLE WORD WRITE TO FLASH PROGRAM MEMORY
MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base address
MOVWF TBLPTRU
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW ; The table pointer must be loaded with an even
address
MOVWF TBLPTRL
MOVLW DATA0 ; LSB of word to be written
MOVWF TABLAT
TBLWT*+
MOVLW DATA1 ; MSB of word to be written
MOVWF TABLAT
TBLWT* ; The last table write must not increment the table
pointer! The table pointer needs to point to the
MSB before starting the write operation.
PROGRAM_MEMORY
BSF EECON1, WPROG ; enable single word write
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, WPROG ; disable single word write
BCF EECON1, WREN ; disable write to memory