PIC16F87XA
An example of the complete four-word write sequence
is shown in Example 3-4. The initial address is loaded
into the EEADRH:EEADR register pair; the four words
of data are loaded using indirect addressing.
EXAMPLE 3-4:
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WRITING TO FLASH PROGRAM MEMORY
This write routine assumes the following:
1. A valid starting address (the least significant bits = ‘00’)is loaded in ADDRH:ADDRL
2. The 8 bytes of data are loaded, starting at the address in DATADDR
3. ADDRH, ADDRL and DATADDR are all located in shared data memory 0x70 - 0x7f
BSF
BCF
MOVF
MOVWF
MOVF
MOVWF
MOVF
MOVWF
MOVF
MOVWF
INCF
MOVF
MOVWF
INCF
BSF
BSF
BSF
BCF
MOVLW
MOVWF
MOVLW
MOVWF
BSF
NOP
NOP
BCF
BSF
BCF
INCF
MOVF
ANDLW
XORLW
BTFSC
GOTO
EECON1,WREN
INTCON,GIE
STATUS,RP0
EEADR,F
EEADR,W
0x03
0x03
STATUS,Z
LOOP
STATUS,RP1
STATUS,RP0
ADDRH,W
EEADRH
ADDRL,W
EEADR
DATAADDR,W
FSR
INDF,W
EEDATA
FSR,F
INDF,W
EEDATH
FSR,F
STATUS,RP0
EECON1,EEPGD
EECON1,WREN
INTCON,GIE
55h
EECON2
AAh
EECON2
EECON1,WR
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Bank 2
Load initial address
Load initial data address
Load first data byte into lower
Next byte
Load second data byte into upper
LOOP
Bank 3
Point to program memory
Enable writes
Disable interrupts (if using)
Start of required write sequence:
Write 55h
Write AAh
Set WR bit to begin write
Any instructions here are ignored as processor
halts to begin write sequence
processor will stop here and wait for write complete
after write processor continues with 3rd instruction
Disable writes
Enable interrupts (if using)
Bank 2
Increment address
Check if lower two bits of address are ‘00’
Indicates when four words have been programmed
Exit if more than four words,
Continue if less than four words
Required
Sequence
DS39582A-page 36
Advance Information
2001 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
