PIC16F688 Datasheet, PDF (76/174 Pages) Microchip Technology – 14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F688
9.1.4
READING THE FLASH PROGRAM
MEMORY
To read a program memory location, the user must
write two bytes of the address to the EEADR and
EEADRH registers, set the EEPGD control bit
(EECON1<7>), and then set control bit RD
(EECON1<0>). 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 immediately following the “BSF
EECON1,RD” instruction to be ignored. The data is
available in the very next cycle, in the EEDAT and
EEDATH registers; therefore, it can be read as two
bytes in the following instructions.
EEDAT and EEDATH registers will hold this value until
another read or until it is written to by the user (during
a write operation).
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, it
will be immediately reset to ‘0’ and no
operation will take place.
EXAMPLE 9-3: FLASH PROGRAM READ
BSF
STATUS, RP0
;
BCF
STATUS, RP1
; Bank 1
MOVLW MS_PROG_EE_ADDR ;
MOVWF EEADRH
; MS Byte of Program Address to read
MOVLW LS_PROG_EE_ADDR ;
MOVWF EEADR
; LS Byte of Program Address to read
BSF
EECON1, EEPGD ; Point to PROGRAM memory
BSF
EECON1, RD
; EE Read
;
; First instruction after BSF EECON1,RD executes normally
NOP
NOP
; Any instructions here are ignored as program
; memory is read in second cycle after BSF EECON1,RD
;
MOVF EEDAT, W
; W = LS Byte of Program EEDAT
MOVF EEDATH, W
; W = MS Byte of Program EEDAT
DS41203B-page 74
Preliminary
 2004 Microchip Technology Inc.