Datasheet

203
ATmega8A [DATASHEET]
8159E–AVR–02/2013
; 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)
rcallDo_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)
rcallDo_spm
; re-enable the RWW section
ldi spmcrval, (1<<RWWSRE) | (1<<SPMEN)
rcallDo_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+
ld r1, Y+
cpse r0, r1
rjmp Error
sbiw loophi:looplo, 1 ;use subi for PAGESIZEB<=256
brne Rdloop
; return to RWW section
; verify that RWW section is safe to read
Return:
in temp1, SPMCR
sbrs temp1, RWWSB ; If RWWSB is set, the RWW section is not ready yet
ret
; re-enable the RWW section
ldi spmcrval, (1<<RWWSRE) | (1<<SPMEN)
rcallDo_spm
rjmp Return
Do_spm:
; check for previous SPM complete
Wait_spm:
in temp1, SPMCR
sbrc temp1, SPMEN
rjmp Wait_spm
; input: spmcrval determines SPM action
; disable interrupts if enabled, store status
in temp2, SREG
cli
; check that no EEPROM write access is present
Wait_ee:
sbic EECR, EEWE
rjmp Wait_ee