attiny13-20ss ATMEL Corporation, attiny13-20ss Datasheet - Page 99

• Manufacturer Part Number: attiny13-20ss
• Description: 8-bit Microcontroller With 1k Bytes In-system Programmable Flash - Atmel Corporation
• Manufacturer: ATMEL Corporation

Addressing the Flash
During Self-
Programming
2535G–AVR–01/07
The Z-pointer is used to address the SPM commands.
Since the Flash is organized in pages (see Table 46 on page 106), 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 53. 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 53. Addressing the Flash During SPM
Note:
Bit
ZH (R31)
ZL (R30)
Z - REGISTER
PROGRAM MEMORY
1. The different variables used in Figure 53 are listed in Table 46 on page 106.
BIT
PAGE
PROGRAM
COUNTER
15
Z15
15
Z7
7
PAGE ADDRESS
WITHIN THE FLASH
ZPCMSB
PCMSB
Z14
14
Z6
6
PCPAGE
Z13
Z5
13
5
ZPAGEMSB
PAGEMSB
PCWORD
Z12
12
Z4
4
WORD ADDRESS
WITHIN A PAGE
(1)
1
Z11
11
Z3
3
0
0
INSTRUCTION WORD
PAGE
Z10
10
Z2
2
Z9
Z1
9
1
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
Z8
Z0
8
0
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