Datasheet

© 2007 Microchip Technology Inc. DS41250F-page 191
PIC16F913/914/916/917/946
13.1.4 READING THE FLASH PROGRAM
MEMORY
To read a program memory location, the user must
write two bytes of the address to the EEADRL and
EEADRH registers, set the EEPGD control bit, and
then set control bit RD of the EECON1 register. Once
the read control bit is set, the program memory Flash
controller will use the second instruction cycle to read
the data. This causes the second instruction immedi-
ately following the “BSF EECON1,RD” instruction to be
ignored. The data is available in the very next cycle, in
the EEDATL and EEDATH registers; therefore, it can
be read as two bytes in the following instructions.
EEDATL and EEDATH registers will hold this value until
another read or until it is written to by the user (during
a write operation).
EXAMPLE 13-3: FLASH PROGRAM READ
Note 1: The two instructions following a program
memory read are required to be NOP’s.
This prevents the user from executing a
two-cycle instruction on the next
instruction after the RD bit is set.
2: If the WR bit is set when EEPGD = 1, the
WR bit will be immediately reset to ‘0’ and
no operation will take place.
BANKSEL EEADRL ;
MOVLW MS_PROG_EE_ADDR;
MOVWF EEADRH ;MS Byte of Program Address to read
MOVLW LS_PROG_EE_ADDR;
MOVWF EEADRL ;LS Byte of Program Address to read
BANKSEL EECON1 ;
BSF EECON1, EEPGD ;Point to PROGRAM memory
BSF EECON1, RD ;EE Read
;
NOP
NOP ;Any instructions here are ignored as program
;memory is read in second cycle after BSF
;
BANKSEL EEDATL ;
MOVF EEDATL, W ;W = LS Byte of EEPROM Data program
MOVWF DATAL ;
MOVF EEDATH, W ;W = MS Byte of EEPROM Data program
MOVWF DATAH ;
Required
Sequence