PIC16F946-ESLASHMLQTP datasheet(193/330 Pages) MICROCHIP

193 / 330 page

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

the

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

;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

;

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