PIC16F819T-E Datasheet, PDF (33/176 Pages) Microchip Technology – 18/20-Pin Enhanced Flash Microcontrollers with nanoWatt Technology

PIC16F818/819
An example of the complete four-word write sequence
is shown in Example 3-5. The initial address is loaded
into the EEADRH:EEADR register pair; the four words
of data are loaded using indirect addressing, assuming
that a row erase sequence has already been
performed.
EXAMPLE 3-5: WRITING TO FLASH PROGRAM MEMORY
; This write routine assumes the following:
; 1. The 32 words in the erase block have already been erased.
; 2. A valid starting address (the least significant bits = '00') is loaded into EEADRH:EEADR
; 3. This example is starting at 0x100, this is an application dependent setting.
; 4. The 8 bytes (4 words) of data are loaded, starting at an address in RAM called ARRAY.
; 5. This is an example only, location of data to program is application dependent.
; 6. word_block is located in data memory.
BANKSEL
BSF
BSF
BCF
EECON1
EECON1, EEPGD
EECON1, WREN
EECON1, FREE
;prepare for WRITE procedure
;point to program memory
;allow write cycles
;perform write only
BANKSEL word_block
MOVLW .4
MOVWF word_block
;prepare for 4 words to be written
LOOP
BANKSEL
MOVLW
MOVWF
MOVLW
MOVWF
BANKSEL
MOVLW
MOVWF
EEADRH
0x01
EEADRH
0x00
EEADR
ARRAY
ARRAY
FSR
BANKSEL
MOVF
MOVWF
INCF
MOVF
MOVWF
INCF
EEDATA
INDF, W
EEDATA
FSR, F
INDF, W
EEDATH
FSR, F
;Start writing at 0x100
;load HIGH address
;load LOW address
;initialize FSR to start of data
;indirectly load EEDATA
;increment data pointer
;indirectly load EEDATH
;increment data pointer
BANKSEL
MOVLW
MOVWF
MOVLW
MOVWF
BSF
NOP
NOP
EECON1
0x55
EECON2
0xAA
EECON2
EECON1, WR
;required sequence
;set WR bit to begin write
;instructions here are ignored as processor
BANKSEL
INCF
BANKSEL
DECFSZ
GOTO
EEADR
EEADR, f
word_block
word_block, f
loop
;load next word address
;have 4 words been written?
;NO, continue with writing
BANKSEL EECON1
BCF
EECON1, WREN
BSF
INTCON, GIE
;YES, 4 words complete, disable writes
;enable interrupts
 2004 Microchip Technology Inc.
DS39598E-page 31