227
2513L–AVR–03/2013
ATmega162/V
Programming Time for
Flash When Using
SPM
The calibrated RC Oscillator is used to time Flash accesses.
Table 92 shows the typical pro-
gramming time for Flash accesses from the CPU.
Simple Assembly
Code Example for a
Boot Loader
;-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.
.equ
PAGESIZEB = PAGESIZE*2
;PAGESIZEB is page size in BYTES, not
; words
.org SMALLBOOTSTART
Write_page:
; page erase
ldi
spmcrval, (1<<PGERS) | (1<<SPMEN)
call
Do_spm
; re-enable the RWW section
ldi
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
call
Do_spm
; transfer data from RAM to Flash page buffer
ldi
looplo, low(PAGESIZEB)
;init loop variable
ldi
loophi, high(PAGESIZEB)
;not required for PAGESIZEB<=256
Wrloop:
ld
r0, Y+
ld
r1, Y+
ldi
spmcrval, (1<<SPMEN)
call
Do_spm
adiw
ZH:ZL, 2
sbiw
loophi:looplo, 2
;use subi for PAGESIZEB<=256
brne
Wrloop
; execute page write
subi
ZL, low(PAGESIZEB)
;restore pointer
sbci
ZH, high(PAGESIZEB)
;not required for PAGESIZEB<=256
ldi
spmcrval, (1<<PGWRT) | (1<<SPMEN)
call
Do_spm
; re-enable the RWW section
ldi
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
call
Do_spm
; read back and check, optional
ldi
looplo, low(PAGESIZEB)
;init loop variable
ldi
loophi, high(PAGESIZEB)
;not required for PAGESIZEB<=256
subi
YL, low(PAGESIZEB)
;restore pointer
sbci
YH, high(PAGESIZEB)
Rdloop:
lpm
r0, Z+
Table 92. SPM Programming Time
Symbol
Min Programming Time
Max Programming Time
Flash Write (Page Erase, Page Write,
and Write Lock bits by SPM)
3.7ms
4.5ms