PIC12F519-ESLASHMS datasheet(24/96 Pages) MICROCHIP

24 / 96 page

PIC12F519

DS41319B-page 22

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.

Load EEADR with the address.

Load EEDATA with the data to write.

Set the WREN bit to enable write access to the

array.

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.

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

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