Datasheet

PIC12F519
DS41319B-page 22 © 2008 Microchip Technology Inc.
5.2.2 WRITING TO FLASH DATA
MEMORY
Once a cell is erased, new data can be written. Pro-
gram execution is suspended during the write cycle.
The following sequence must be performed for a single
byte write.
1. Load EEADR with the address.
2. Load EEDATA with the data to write.
3. Set the WREN bit to enable write access to the
array.
4. Set the WR bit to initiate the erase cycle.
If the WR bit is not set in the instruction cycle after the
WREN bit is set, the WREN bit will be cleared in
hardware.
Sample code that follows this procedure is included in
Example 3.
EXAMPLE 3: WRITING A FLASH DATA
MEMORY ROW
5.3 Write Verify
Depending on the application, good programming
practice may dictate that data written to the Flash data
memory be verified. Example 4 is an example of a write
verify.
EXAMPLE 4: WRITE VERIFY OF DATA
EEPROM
5.4 Code Protection
Code protection does not prevent the CPU from per-
forming read or write operations on the Flash data
memory. Refer to the code protection chapter for more
information.
Note 1: Only a series of BSF commands will work
to enable the memory write sequence
documented in Example 2. No other
sequence of commands will work, no
exceptions.
2: For reads, erases and writes to the Flash
data memory, there is no need to insert a
NOP into the user code as is done on
mid-range devices. The instruction imme-
diately following the “BSF
EECON,WR/RD” will be fetched and
executed properly.
BANKSEL EEADR
MOVLW EE_ADR_WRITE ; LOAD ADDRESS
MOVWF EEADR ;
MOVLW EE_DATA_TO_WRITE ; LOAD DATA
MOVWF EEDATA ; INTO EEDATA REGISTER
BSF EECON,WREN ; ENABLE WRITES
BSF EECON,WR ; INITITATE ERASE
MOVF EEDATA, W ;EEDATA has not changed
;from previous write
BSF EECON, RD ;Read the value written
XORWF EEDATA, W ;
BTFSS STATUS, Z ;Is data the same
GOTO WRITE_ERR ;No, handle error
;Yes, continue