Datasheet

 2003-2013 Microchip Technology Inc. DS39609C-page 69
PIC18F6520/8520/6620/8620/6720/8720
EXAMPLE 5-3: WRITING TO FLASH PROGRAM MEMORY (CONTINUED)
5.5.2 WRITE VERIFY
Depending on the application, good programming
practice may dictate that the value written to the mem-
ory should be verified against the original value. This
should be used in applications where excessive writes
can stress bits near the specification limit.
5.5.3 UNEXPECTED TERMINATION OF
WRITE OPERATION
If a write is terminated by an unplanned event, such as
loss of power or an unexpected Reset, the memory
location just programmed should be verified and repro-
grammed if needed. The WRERR bit is set when a
write operation is interrupted by a MCLR
Reset, or a
WDT Time-out Reset during normal operation. In these
situations, users can check the WRERR bit and rewrite
the location.
5.5.4 PROTECTION AGAINST
SPURIOUS WRITES
To protect against spurious writes to Flash program
memory, the write initiate sequence must also be
followed. See Section 23.0 “Special Features of the
CPU” for more detail.
5.6 Flash Program Operation During
Code Protection
See Section 23.0 “Special Features of the CPU” for
details on code protection of Flash program memory.
TABLE 5-2: REGISTERS ASSOCIATED WITH PROGRAM FLASH MEMORY
PROGRAM_MEMORY
BSF EECON1, EEPGD ; point to Flash program memory
BCF EECON1, CFGS ; access Flash program memory
BSF EECON1, WREN ; enable write to memory
BCF INTCON, GIE ; disable interrupts
MOVLW 55h
MOVWF EECON2 ; write 55H
Required MOVLW AAh
Sequence MOVWF EECON2 ; write AAH
BSF EECON1, WR ; start program (CPU stall)
NOP
BSF INTCON, GIE ; re-enable interrupts
DECFSZ COUNTER_HI ; loop until done
BRA PROGRAM_LOOP
BCF EECON1, WREN ; disable write to memory
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on
POR, BOR
Value on
all other
Resets
TBLPTRU
— — bit 21 Program Memory Table Pointer Upper Byte
(TBLPTR<20:16>)
--00 0000 --00 0000
TBPLTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 0000 0000 0000 0000
TBLPTRL Program Memory Table Pointer High Byte (TBLPTR<7:0>) 0000 0000 0000 0000
TABLAT Program Memory Table Latch 0000 0000 0000 0000
INTCON GIE/GIEH PEIE/GIEL
TMR0IE INTE RBIE TMR0IF INTF RBIF 0000 0000 0000 0000
EECON2 EEPROM Control Register 2 (not a physical register) — —
EECON1 EEPGD CFGS — FREE WRERR WREN WR
RD xx-0 x000 uu-0 u000
IPR2
— CMIP —EEIPBCLIP LVDIP TMR3IP CCP2IP ---1 1111 ---1 1111
PIR2
— CMIF —EEIFBCLIF LVDIF TMR3IF CCP2IF ---0 0000 ---0 0000
PIE2
— CMIE —EEIEBCLIE LVDIE TMR3IE CCP2IE ---0 0000 ---0 0000
Legend: x = unknown, u = unchanged, r = reserved, - = unimplemented, read as ‘0’.
Shaded cells are not used during Flash/EEPROM access.