Datasheet

Table Of Contents
© 2007 Microchip Technology Inc. DS39605F-page 65
PIC18F1220/1320
EXAMPLE 6-3: WRITING TO FLASH PROGRAM MEMORY (CONTINUED)
6.5.2 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.
6.5.3 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.
6.6 Flash Program Operation During
Code Protection
See Section 19.0 “Special Features of the CPU” for
details on code protection of Flash program memory.
TABLE 6-2: REGISTERS ASSOCIATED WITH PROGRAM FLASH MEMORY
WRITE_WORD_TO_HREGS
MOVF POSTINC0, W ; get low byte of buffer data and increment FSR0
MOVWF TABLAT ; present data to table latch
TBLWT+* ; short write
; to internal TBLWT holding register, increment
TBLPTR
DECFSZ COUNTER ; loop until buffers are full
GOTO WRITE_WORD_TO_HREGS
PROGRAM_MEMORY
BCF INTCON, GIE ; disable interrupts
MOVLW 55h ; required sequence
MOVWF EECON2 ; write 55H
MOVLW AAh
MOVWF EECON2 ; write AAH
BSF EECON1, WR ; start program (CPU stall)
NOP
BSF INTCON, GIE ; re-enable interrupts
DECFSZ COUNTER_HI ; loop until done
GOTO 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 000x 0000 000u
EECON2 EEPROM Control Register 2 (not a physical register)
——
EECON1 EEPGD CFGS FREE WRERR WREN WR RD xx-0 x000 uu-0 u000
IPR2 OSCFIP
—EEIP LVDIP TMR3IP 1--1 -11- 1--1 -11-
PIR2 OSCFIF
—EEIF LVDIF TMR3IF 0--0 -00- 0--0 -00-
PIE2 OSCFIE
—EEIE LVDIE TMR3IE 0--0 -00- 0--0 -00-
Legend: x = unknown, u = unchanged, – = unimplemented, read as ‘0’.
Shaded cells are not used during Flash/EEPROM access.