atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 280

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

23.7
280
Self-Programming the Flash
ATmega32/64/M1/C1
Figure 23-3. 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 example
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 alter-
native 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. It is essential that
the page address used in both the Page Erase and Page Write operation is addressing the
same page. See
assembly code example.
Fill temporary page buffer
Perform a Page Erase
Perform a Page Write
Perform a Page Erase
Fill temporary page buffer
Perform a Page Write
Z - REGISTER
1. The different variables used in
PROGRAM MEMORY
BIT
PAGE
PROGRAM
COUNTER
15
“Simple Assembly Code Example for a Boot Loader” on page 284
PAGE ADDRESS
WITHIN THE FLASH
ZPCMSB
PCMSB
PCPAGE
Figure 23-3
ZPAGEMSB
PAGEMSB
PCWORD
WORD ADDRESS
WITHIN A PAGE
(1)
are listed in
1
0
0
INSTRUCTION WORD
PAGE
Table 23-9 on page
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
286.
7647A–AVR–02/08
for an