PIC16F870-I/SP View Datasheet(PDF) - Microchip Technology
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Description
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PIC16F870-I/SP Datasheet PDF : 156 Pages
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PIC16F870/871
4.6 Writing to the FLASH Program
Memory
When the PIC16F870/871 are fully code protected or
not code protected, a word of the FLASH program
memory may be written provided the WRT configura-
tion bit is set. If the PIC16F870/871 are partially code
protected, then a word of FLASH program memory
may be written if the word is in a non-code protected
segment of memory and the WRT configuration bit is
set. To write a FLASH program location, the first two
bytes of the address must be written to the EEADR and
EEADRH registers and two bytes of the data to the
EEDATA and EEDATH registers, set the EEPGD con-
trol bit (EECON1<7>), and then set control bit WR
(EECON1<1>). The sequence in Example 4-4 must be
followed to initiate a write to program memory.
The microcontroller will then halt internal operations
during the next two instruction cycles for the TPEW
(parameter D133) in which the write takes place. This
is not SLEEP mode, as the clocks and peripherals will
continue to run. Therefore, the two instructions follow-
ing the “BSF EECON, WR” should be NOP instructions.
After the write cycle, the microcontroller will resume
operation with the 3rd instruction after the EECON1
write instruction.
EXAMPLE 4-4:
FLASH PROGRAM WRITE
BSF
STATUS, RP1
;
BCF
STATUS, RP0
; Bank 2
MOVLW ADDRH
;
MOVWF EEADRH
; MSByte of Program Address to read
MOVLW ADDRL
;
MOVWF EEADR
; LSByte of Program Address to read
MOVLW DATAH
;
MOVWF EEDATH
; MS Program Memory Value to write
MOVLW DATAL
;
MOVWF EEDATA
; LS Program Memory Value to write
BSF
STATUS, RP0
; Bank 3
BSF
EECON1, EEPGD ; Point to PROGRAM memory
BSF
EECON1, WREN
; Enable writes
Required
Sequence
BCF
MOVLW
MOVWF
MOVLW
MOVWF
BSF
INTCON, GIE
55h
EECON2
AAh
EECON2
EECON1, WR
; Disable Interrupts
;
; Write 55h
;
; Write AAh
; Set WR bit to begin write
NOP
NOP
BSF INTCON, GIE
BCF EECON1, WREN
; Instructions here are ignored by the microcontroller
; Microcontroller will halt operation and wait for
; a write complete. After the write
; the microcontroller continues with 3rd instruction
; Enable Interrupts
; Disable writes
© 1999 Microchip Technology Inc.
Preliminary
DS30569A-page 43
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