
164
8197C–AVR–05/11
ATtiny261A/461A/861A
If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded will be
lost.
17.3
Performing a Page Write
To execute Page Write, set up the address in the Z-pointer, write “00000101” to SPMCSR and
execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored.
The page address must be written to PCPAGE. Other bits in the Z-pointer must be written to
zero during this operation.
Note:
The CPU is halted during the Page Write operation.
17.4
Addressing the Flash During Self-Programming
The Z-pointer is used to address the SPM commands.
be treated as having two different sections. One section, consisting of the least significant bits, is
addressing the words within a page, while the most significant bits are addressing the pages.
This is shown in
Figure 17-1. Note that the Page Erase and Page Write operations are
addressed independently. Therefore it is of major importance that the software addresses the
same page in both the Page Erase and Page Write operation.
The LPM instruction uses the Z-pointer to store the address. Since this instruction addresses the
Flash byte-by-byte, also the LSB (bit Z0) of the Z-pointer is used.
Figure 17-1.
Addressing the Flash During SPM
Note:
Bit
1514
1312
1110
9
8
ZH (R31)
Z15
Z14
Z13
Z12
Z11
Z10
Z9
Z8
ZL (R30)
Z7Z6
Z5Z4Z3
Z2Z1
Z0
765
43
21
0
PROGRAM MEMORY
0
1
15
Z - REGISTER
BIT
0
ZPAGEMSB
WORD ADDRESS
WITHIN A PAGE
PAGE ADDRESS
WITHIN THE FLASH
ZPCMSB
INSTRUCTION WORD
PAGE
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
PAGE
PCWORD
PCPAGE
PCMSB
PAGEMSB
PROGRAM
COUNTER