ATMEGA168PA-PU Atmel, ATMEGA168PA-PU Datasheet - Page 275

MCU, 8BIT, AVR, 16K FLASH, 28PDIP

ATMEGA168PA-PU

Manufacturer Part Number
ATMEGA168PA-PU
Description
MCU, 8BIT, AVR, 16K FLASH, 28PDIP
Manufacturer
Atmel
Datasheet

Specifications of ATMEGA168PA-PU

Controller Family/series
Atmega
No. Of I/o's
23
Eeprom Memory Size
512Byte
Ram Memory Size
1KB
Cpu Speed
20MHz
No.
RoHS Compliant
Core Size
8bit
Program Memory Size
16KB
Oscillator Type
External, Internal
Rohs Compliant
Yes

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Part Number:
ATMEGA168PA-PU
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25.2.5
8271C–AVR–08/10
Simple Assembly Code Example for a Boot Loader
Note that the RWWSB bit will always be read as zero in ATmega 48A/48PA. Nevertheless, it is
recommended to check this bit as shown in the code example, to ensure compatibility with
devices supporting Read-While-Write.
ATmega48A/48PA/88A/88PA/168A/168PA/328/328
.equ PAGESIZEB = PAGESIZE*2
.org SMALLBOOTSTART
Write_page:
Wrloop:
;-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
rcallDo_spm
; re-enable the RWW section
ldi
rcallDo_spm
; transfer data from RAM to Flash page buffer
ldi
ldi
ld
ld
ldi
rcallDo_spm
adiw ZH:ZL, 2
sbiw loophi:looplo, 2
brne Wrloop
; execute Page Write
subi ZL, low(PAGESIZEB)
sbci ZH, high(PAGESIZEB)
ldi
rcallDo_spm
; re-enable the RWW section
ldi
rcallDo_spm
; read back and check, optional
ldi
ldi
subi YL, low(PAGESIZEB)
spmcrval, (1<<PGERS) | (1<<SELFPRGEN)
spmcrval, (1<<RWWSRE) | (1<<SELFPRGEN)
looplo, low(PAGESIZEB)
loophi, high(PAGESIZEB)
r0, Y+
r1, Y+
spmcrval, (1<<SELFPRGEN)
spmcrval, (1<<PGWRT) | (1<<SELFPRGEN)
spmcrval, (1<<RWWSRE) | (1<<SELFPRGEN)
looplo, low(PAGESIZEB)
loophi, high(PAGESIZEB)
;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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