VojtVojtěěchch KrmKrmííččekek
vojtec@vojtec@icsics..munimuni..czcz
PIC12F629 / 675
EEPROM
PIC12FPIC12F629 / 675629 / 675
EEPROMEEPROM
PackagePackage
EEPROMEEPROM -- BBasicsasics
Readable and writable duringReadable and writable during
normal voltage,normal voltage,
memory is not directly accessible,memory is not directly accessible,
itit’’s mapped in the register file space,s mapped in the register file space,
there are four control registers:there are four control registers:
EECON1, EECON2, EEDATA, EEADREECON1, EECON2, EEDATA, EEADR
addressaddress rangerange fromfrom 0h to 7Fh0h to 7Fh
interruptinterrupt onon writewrite completecomplete (EEIF)(EEIF)
RegistersRegisters EepromEeprom
RegistersRegisters EepromEeprom (cont.)(cont.)
Read sequenceRead sequence
bsf STATUS,RP0 ;Bank 1
movlw ADDRESS ;
movwf EEADR ;Address to read
bsf EECON1,RD ;EE Read
movfmovf EEDATA,WEEDATA,W ;Move data to W
Write sequenceWrite sequence
bsf STATUS,RP0 ;Bank 1
movlw <value>
movwf EEDATA ; Data to write
movlw <address>
movwf EEADR ; Address to write
bsf EECON1,WREN ; Enable write
bcf INTCON,GIE ; Disable INTs
movlw 0x55 ; Unlock write
movwf EECON2 ;
movlw 0xAA ;
movwf EECON2 ;
bsfbsf EECON1,WREECON1,WR ; Start the write
Loop:
btfsc EECON1,WR ; Waiting until
goto Loop ; write is finished
bsf INTCON,GIE ; Enable INTS
Verify sequenceVerify sequence
bcf STATUS,RP0 ;Bank 0
: ;Any code
bsf STATUS,RP0 ;Bank 1 READ
movf EEDATA,W ;EEDATA not
changed from previous write
bsf EECON1,RD ;<Y>, Read the
;value written
xorwf EEDATA,W
btfss STATUS,Z ;Is data the same
goto WRITE_ERR ;<N> handle error
: ;<Y>, continue
EEPROMEEPROM RegistersRegisters