ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 283

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

27.8
9223B–AVR–09/11
Self-Programming the Flash
Figure 27-3. Addressing the Flash During SPM
Note:
The program memory is updated in a page by page fashion. Before programming a page with
the data stored in the temporary page buffer, the page must be erased. The temporary page
buffer is filled one word at a time using SPM and the buffer can be filled either before the Page
Erase command or between a Page Erase and a Page Write operation:
Alternative 1, fill the buffer before a Page Erase
Alternative 2, fill the buffer after Page Erase
If only a part of the page needs to be changed, the rest of the page must be stored (for exam-
ple in the temporary page buffer) before the erase, and then be rewritten. When using
alternative 1, the Boot Loader provides an effective Read-Modify-Write feature which allows
the user software to first read the page, do the necessary changes, and then write back the
modified data. If alternative 2 is used, it is not possible to read the old data while loading since
the page is already erased. The temporary page buffer can be accessed in a random
sequence.
Z - REGISTER
• Fill temporary page buffer
• Perform a Page Erase
• Perform a Page Write
• Perform a Page Erase
• Fill temporary page buffer
• Perform a Page Write
Atmel ATmega48PA/88PA/168PA [Preliminary]
PROGRAM MEMORY
1. The different variables used in
BIT
PROGRAM
COUNTER
PAGE
15
PAGE ADDRESS
WITHIN THE FLASH
ZPCMSB
PCMSB
PCPAGE
Figure 27-3
ZPAGEMSB
PAGEMSB
PCWORD
WORD ADDRESS
WITHIN A PAGE
(1)
are listed in
1
0
0
INSTRUCTION WORD
PAGE
Table 27-9 on page
PCWORD[PAGEMSB:0]:
00
01
02
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