
184
8008H–AVR–04/11
ATtiny48/88
19.0.3
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.
The CPU is halted during the Page Write operation.
19.1
Addressing the Flash During Self-Programming
The Z-pointer is used to address the SPM commands.
Counter can be treated as having two different sections. One section, consisting of the least sig-
nificant bits, is addressing the words within a page, while the most significant bits are addressing
the pages. This is shown in
Figure 19-1. 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 19-1. Addressing the Flash During SPM
Note:
Bit
151413121110
9
8
ZH (R31)
Z15
Z14
Z13
Z12
Z11
Z10
Z9
Z8
ZL (R30)
Z7Z6Z5
Z4Z3Z2Z1
Z0
76543210
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