PIC16F526-ISLASHP datasheet(24/122 Pages) MICROCHIP

24 / 122 page

PIC16F526

DS41326D-page 24

 2010 Microchip Technology Inc.

5.2.2

WRITING TO FLASH DATA

MEMORY

Once a cell is erased, new data can be written.

Program 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 FLASH

DATA MEMORY

EEDATA: FLASH DATA REGISTER

EEADR: FLASH ADDRESS REGISTER

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

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 immediately

following the “BSF EECON,WR/RD” will be

fetched and executed properly.

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

R/W-x

EEDATA7

EEDATA6

EEDATA5

EEDATA4

EEDATA3

EEDATA2

EEDATA1

EEDATA0

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7-0

EEDATA<7:0>: 8-bits of data to be read from/written to data Flash

U-0

R/W-x

—

EEADR5

EEADR4

EEADR3

EEADR2

EEADR1

EEADR0

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7-6

Unimplemented: Read as ‘0’.

bit 5-0

EEADR<5:0>: 6-bits of data to be read from/written to data Flash

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