Datasheet

154
ATtiny2313/V
2543H–AVR–02/05
Addressing the Flash
During Self-
Programming
The Z-pointer is used to address the SPM commands.
Since the Flash is organized in pages (see Table 69 on page 160), the Program 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 68. 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 68. Addressing the Flash During SPM
(1)
Note: 1. The different variables used in Figure 68 are listed in Table 69 on page 160.
Bit 151413121110 9 8
ZH (R31) Z15 Z14 Z13 Z12 Z11 Z10 Z9 Z8
ZL (R30) Z7Z6Z5Z4Z3Z2Z1Z0
76543210
PROGRAM MEMORY
0115
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
PCWORDPCPAGE
PCMSB
PAGEMSB
PROGRAM
COUNTER