Addressing the flash during self- programming, Attiny2313 – Rainbow Electronics ATtiny2313 User Manual
Page 156
156
ATtiny2313
2543A–AVR–08/03
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 74 on page 164), 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 67. 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 67. Addressing the Flash During SPM
(1)
Note:
1. The different variables used in Figure 67 are listed in Table 74 on page 164.
Bit
15
14
13
12
11
10
9
8
ZH (R31)
Z15
Z14
Z13
Z12
Z11
Z10
Z9
Z8
ZL (R30)
Z7
Z6
Z5
Z4
Z3
Z2
Z1
Z0
7
6
5
4
3
2
1
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