PIC16F688
EEDAT and EEDATH registers will hold this value until
another read or until it is written to by the user (during
a write operation).
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.
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
BCF
STATUS, RP0
STATUS, RP1
MS_PROG_EE_ADDR
EEADRH
LS_PROG_EE_ADDR
EEADR
EECON1, EEPGD
EECON1, RD
;
; Bank 1
;
MOVLW
MOVWF
MOVLW
MOVWF
BSF
; MS Byte of Program Address to read
;
; LS Byte of Program Address to read
; Point to PROGRAM memory
; EE Read
BSF
;
;
; 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
MOVF
EEDAT, W
EEDATH, W
; W = LS Byte of Program EEDAT
; W = MS Byte of Program EEDAT
DS41203B-page 74
Preliminary
2004 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
