ATMEGA48V_11 ATMEL [ATMEL Corporation], ATMEGA48V_11 Datasheet - Page 279

• Manufacturer Part Number: ATMEGA48V_11
• Description: 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

27.8.11
27.8.12
2545T–AVR–05/11
Programming time for flash when using SPM
Simple assembly code example for a boot loader
The calibrated RC Oscillator is used to time Flash accesses.
gramming time for Flash accesses from the CPU.
Table 27-5.
Note:
Flash write (page erase, page write, and
write lock bits by SPM)
.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
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
1. Minimum and maximum programming time is per individual operation.
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)
SPM programming time
Symbol
(1)
.
;PAGESIZEB is page size in BYTES, not words
Min. programming time
;init loop variable
;not required for PAGESIZEB<=256
;use subi for PAGESIZEB<=256
;restore pointer
;not required for PAGESIZEB<=256
3.7ms
ATmega48/88/168
Table 27-5
Max. programming time
shows the typical pro-
4.5ms
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