PIC18F2450/4450
2006 Microchip Technology Inc.
Advance Information
DS39760A-page 81
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
memory 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
reprogrammed if needed. If the write operation is
interrupted by a MCLR Reset or a WDT Time-out Reset
during normal operation, the user can check the
WRERR bit and rewrite the location(s) as needed.
6.5.4
PROTECTION AGAINST SPURIOUS
WRITES
To protect against spurious writes to Flash program
memory, the write initiate sequence must also be
6.6
Flash Program Operation During
Code Protection
program memory.
TABLE 6-2:
REGISTERS ASSOCIATED WITH PROGRAM FLASH MEMORY
PROGRAM_MEMORY
BCF
EECON1, CFGS
; access Flash program memory
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 0AAh
BSF
EECON1, WR
; start program (CPU stall)
DECFSZ
COUNTER1
BRA
WRITE_BUFFER_BACK
BSF
INTCON, GIE
; re-enable interrupts
BCF
EECON1, WREN
; disable write to memory
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
Values
on page
TBLPTRU
—
bit 21
Program Memory Table Pointer Upper Byte (TBLPTR<20:16>)
TBPLTRH
Program Memory Table Pointer High Byte (TBLPTR<15:8>)
TBLPTRL
Program Memory Table Pointer Low Byte (TBLPTR<7:0>)
TABLAT
Program Memory Table Latch
INTCON
GIE/GIEH PEIE/GIEL TMR0IE
INT0IE
RBIE
TMR0IF
INT0IF
RBIF
EECON2
Control Register 2 (not a physical register)
EECON1
—CFGS
—
FREE
WRERR
WREN
WR
IPR2
OSCFIP
—
USBIP
—
HLVDIP
—
PIR2
OSCFIF
—
USBIF
—
HLVDIF
—
PIE2
OSCFIE
—
USBIE
—
HLVDIE
—
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash access.