Microchip Technology DM164134 Data Sheet

© 2006 Microchip Technology Inc.

DS41159E-page 73

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.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.

6.5.4

PROTECTION AGAINST SPURIOUS 
WRITES

To reduce the probability against spurious writes to
Flash program memory, the write initiate sequence
must also be followed. See Section 24.0 “Special
Features of the CPU” for more detail.

See Section 24.0 “Special Features of the CPU” for
details on code protection of Flash program memory.

WRITE_WORD_TO_HREGS

MOVFW

POSTINC0, W

; get low byte of buffer data

MOVWF

TABLAT

 

; present data to table latch

TBLWT+* 

; write data, perform a short write 

; to internal TBLWT holding register.

DECFSZ

COUNTER 

; loop until buffers are full

BRA

WRITE_WORD_TO_HREGS

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

; write 55h

MOVWF

EECON2

MOVLW

0AAh

; write 0AAh

MOVWF

EECON2 

; start program (CPU stall)

BSF

EECON1, WR

NOP

BSF

INTCON, GIE

; re-enable interrupts

DECFSZ

COUNTER_HI

; loop until done

BRA PROGRAM_LOOP

BCF

EECON1, WREN

; disable write to memory