ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 277

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

26.8.12
8285D–AVR–06/11
Boot Loader: Simple Assembly Code Example
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
.equ PAGESIZEB = PAGESIZE*2
.org SMALLBOOTSTART
Write_page:
Wrloop:
Rdloop:
;-the routine writes one page of data from RAM to Flash
; the first data location in RAM is pointed to by the Y pointer
; the first data location in Flash is pointed to by the Z-pointer
;-error handling is not included
;-the routine must be placed inside the Boot space
; (at least the Do_spm sub routine). Only code inside NRWW section can
; be read during Self-Programming (Page Erase and Page Write).
;-registers used: r0, r1, temp1 (r16), temp2 (r17), looplo (r24),
; loophi (r25), spmcrval (r20)
; storing and restoring of registers is not included in the routine
; register usage can be optimized at the expense of code size
;-It is assumed that either the interrupt table is moved to the Boot
; loader section or that the interrupts are disabled.
; Page Erase
ldi
call Do_spm
; re-enable the RWW section
ldi
call Do_spm
; transfer data from RAM to Flash page buffer
ldi
ldi
ld
ld
ldi
call Do_spm
adiw ZH:ZL, 2
sbiw loophi:looplo, 2
brne Wrloop
; execute Page Write
subi ZL, low(PAGESIZEB)
sbci ZH, high(PAGESIZEB)
ldi
call Do_spm
; re-enable the RWW section
ldi
call Do_spm
; read back and check, optional
ldi
ldi
subi YL, low(PAGESIZEB)
sbci YH, high(PAGESIZEB)
lpm
ld
cpse r0, r1
jmp
spmcrval, (1<<PGERS) | (1<<SPMEN)
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
looplo, low(PAGESIZEB)
loophi, high(PAGESIZEB)
r0, Y+
r1, Y+
spmcrval, (1<<SPMEN)
spmcrval, (1<<PGWRT) | (1<<SPMEN)
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
looplo, low(PAGESIZEB)
loophi, high(PAGESIZEB)
r0, Z+
r1, Y+
Error
;PAGESIZEB is page size in BYTES, not words
;init loop variable
;not required for PAGESIZEB<=256
;use subi for PAGESIZEB<=256
;restore pointer
;not required for PAGESIZEB<=256
;init loop variable
;not required for PAGESIZEB<=256
;restore pointer
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