PIC16F1933-ESLASHP datasheet(327/418 Pages) MICROCHIP

327 / 418 page

Preliminary

DS41364A-page 325

PIC16F193X/LF193X

23.1.2

READING THE DATA EEPROM

MEMORY

To read a data memory location, the user must write the

address to the EEADRL register, clear the EEPGD and

CFGS control bits of the EECON1 register, and then

set control bit RD. The data is available at the very next

cycle, in the EEDATL register; therefore, it can be read

in the next instruction. EEDATL will hold this value until

another read or until it is written to by the user (during

a write operation).

EXAMPLE 23-1:

DATA EEPROM READ

23.1.3

WRITING TO THE DATA EEPROM

MEMORY

To write an EEPROM data location, the user must first

write the address to the EEADRL register and the data

to the EEDATL register. Then the user must follow a

specific sequence to initiate the write for each byte.

The write will not initiate if the above sequence is not

followed exactly (write 55h to EECON2, write AAh to

EECON2, then set WR bit) for each byte. Interrupts

should be disabled during this code segment.

Additionally, the WREN bit in EECON1 must be set to

enable write. This mechanism prevents accidental

writes to data EEPROM due to errant (unexpected)

code execution (i.e., lost programs). The user should

keep the WREN bit clear at all times, except when

updating EEPROM. The WREN bit is not cleared

by hardware.

After a write sequence has been initiated, clearing the

WREN bit will not affect this write cycle. The WR bit will

be inhibited from being set unless the WREN bit is set.

At the completion of the write cycle, the WR bit is

cleared in hardware and the EE Write Complete

Interrupt Flag bit (EEIF) is set. The user can either

enable this interrupt or poll this bit. EEIF must be

cleared by software.

EXAMPLE 23-2:

DATA EEPROM WRITE

Note:

Data EEPROM can be read regardless of

the setting of the CPD bit.

BANKSEL EEADRL

;

MOVLW

DATA_EE_ADDR ;

MOVWF

EEADRL

;Data Memory

;Address to read

BCF

EECON1, CFGS ;Deselect Config space

BCF

EECON1, EEPGD;Point to DATA memory

BSF

EECON1, RD

;EE Read

MOVF

EEDATL, W

;W = EEDATL

BCF

STATUS, RP1

;Bank 0

BANKSEL

EEADRL

;

MOVLW

DATA_EE_ADDR

;

MOVWF

EEADRL

;Data Memory Address to write

MOVLW

DATA_EE_DATA

;

MOVWF

EEDATL

;Data Memory Value to write

BCF

EECON1, CFGS

;Deselect Configuration space

BCF

EECON1, EEPGD

;Point to DATA memory

BSF

EECON1, WREN

;Enable writes

BCF

INTCON, GIE

;Disable INTs.

BTFSC

INTCON, GIE

;SEE AN576

GOTO

$-2

MOVLW

55h

;

MOVWF

EECON2

;Write 55h

MOVLW

AAh

;

MOVWF

EECON2

;Write AAh

BSF

EECON1, WR

;Set WR bit to begin write

BCF

EECON1, WREN

;Disable writes

BTFSC

EECON1, WR

;Wait for write to complete

GOTO

$-2

;Done

PIC16F1933-E/P Datasheet(PDF) 327 Page - Microchip Technology

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