Microchip Technology DM183037 데이터 시트

 2012 Microchip Technology Inc.

DS30575A-page 151

7.5.2

FLASH PROGRAM MEMORY WRITE 
SEQUENCE (WORD PROGRAMMING)

The PIC18F97J94 family of devices has a feature that
allows programming a single word (two bytes). This
feature is enabled when the WWPROG 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 WWPROG bit (EECON1<5>) to
select Word Write mode.

4.

Disable interrupts.

5.

Write 55h to EECON2.

6.

Write 0AAh to EECON2.

7.

Set the WR bit; this will begin the write cycle.

8.

The CPU will stall for the duration of the write for
T

IW 

(see Parameter 

9.

Re-enable interrupts.

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, WWPROG 

; 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 AAh

BSF 

EECON1, WR 

; start program (CPU stall)

BSF

INTCON, GIE 

; re-enable interrupts

BCF

EECON1, WWPROG 

; disable single word write

BCF

EECON1, WREN 

; disable write to memory