PIC16F913 datasheet(159/272 Pages) MICROCHIP

159 / 272 page

Preliminary

DS41250E-page 157

PIC16F917/916/914/913

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

(EECON1<7>),

and

then

set

control

bit

(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 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

the

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.

BSF

STATUS, RP1

;

BCF

STATUS, RP0

; Bank 2

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

STATUS, RP0

; Bank 3

BSF

EECON1, EEPGD

; Point to PROGRAM memory

BSF

EECON1, RD

; EE Read

;

NOP

; Any instructions here are ignored as program

; memory is read in second cycle after BSF EECON1,RD

;

BCF

STATUS, RP0

; Bank 2

MOVF

EEDATA, W

; W = LS Byte of Program EEDATA

MOVWF

DATAL

;

MOVF

EEDATH, W

; W = MS Byte of Program EEDATA

MOVWF

DATAH

;

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