PIC18F2455_07 Datasheet, PDF (89/430 Pages) Microchip Technology – 28/40/44-Pin, High Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
EXAMPLE 6-3:
PROGRAM_MEMORY
Required
Sequence
WRITING TO FLASH PROGRAM MEMORY (CONTINUED)
BSF
BCF
BSF
BCF
MOVLW
MOVWF
MOVLW
MOVWF
BSF
DECFSZ
BRA
BSF
BCF
EECON1, EEPGD
EECON1, CFGS
EECON1, WREN
INTCON, GIE
55h
EECON2
0AAh
EECON2
EECON1, WR
COUNTER1
WRITE_BUFFER_BACK
INTCON, GIE
EECON1, WREN
; point to Flash program memory
; access Flash program memory
; enable write to memory
; disable interrupts
; write 55h
; write 0AAh
; start program (CPU stall)
; re-enable interrupts
; disable write to memory
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 repro-
grammed 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
followed. See Section 25.0 “Special Features of the
CPU” for more detail.
6.6 Flash Program Operation During
Code Protection
See Section 25.5 “Program Verification and Code
Protection” for details on code protection of Flash
program memory.
TABLE 6-2: REGISTERS ASSOCIATED WITH PROGRAM FLASH 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⁽¹⁾ Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) 51
TBLPTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>)
51
TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>)
51
TABLAT Program Memory Table Latch
51
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE
RBIE TMR0IF INT0IF
RBIF
51
EECON2 EEPROM Control Register 2 (not a physical register)
53
EECON1 EEPGD CFGS
—
FREE WRERR WREN
WR
RD
53
IPR2
OSCFIP CMIP USBIP EEIP
BCLIP HLVDIP TMR3IP CCP2IP
54
PIR2
OSCFIF CMIF USBIF EEIF
BCLIF HLVDIF TMR3IF CCP2IF
54
PIE2
OSCFIE CMIE USBIE EEIE
BCLIE HLVDIE TMR3IE CCP2IE
54
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access.
Note 1: Bit 21 of the TBLPTRU allows access to the device Configuration bits.
© 2007 Microchip Technology Inc.
Preliminary
DS39632D-page 87