Datasheet

ATmega164A/PA/324A/PA/644A/PA/1284/P
 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 291
26.8.16 ATmega644A/ATmega644PA Boot Loader parameters
In Table 26-13 through Table 26-15, the parameters used in the description of the Self-Programming are given.
Note: 1. The different BOOTSZ Fuse configurations are shown in Figure 26-2 on page 280.
Note: 1. For details about these two section, see ”NRWW – No Read-While-Write Section” on page 278 and ”RWW – Read-
While-Write Section” on page 278.
Note: 1. Z0: should be zero for all SPM commands, byte select for the (E)LPM instruction.
See ”Addressing the Flash During Self-Programming” on page 282 for details about the use of Z-pointer during Self-
Programming.
Table 26-13. Boot size configuration
(1)
BOOTSZ1 BOOTSZ0 Boot size Pages
Application
flash section
Boot loader
flash section
End
application
section
Boot reset
address
(start boot
loader section)
1 1 512 words 4 0x0000 - 0x7DFF 0x7E00 - 0x7FFF 0x7DFF 0x7E00
1 0 1024 words 8 0x0000 - 0x7BFF 0x7C00 - 0x7FFF 0x7BFF 0x7C00
0 1 2048 words 16 0x0000 - 0x77FF 0x7800 - 0x7FFF 0x77FF 0x7800
0 0 4096 words 32 0x0000 - 0x6FFF 0x7000 - 0x7FFF 0x6FFF 0x7000
Table 26-14. Read-While-Write limit
(1)
Section Pages Address
Read-While-Write section (RWW) 224 0x0000 - 0x6FFF
No Read-While-Write section (NRWW) 32 0x7000 - 0x7FFF
Table 26-15. Explanation of different variables used in Figure 26-3 on page 282 and the mapping to the Z-pointer
Variable
Corresponding
Z-value
Description
(1)
PCMSB 14
Most significant bit in the Program Counter. (The Program Counter is 14 bits
PC[14:0])
PAGEMSB 6
Most significant bit which is used to address the words within one page (128
words in a page requires seven bits PC [6:0]).
ZPCMSB Z15
Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not used, the
ZPCMSB equals PCMSB + 1.
ZPAGEMSB Z7
Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not used, the
ZPAGEMSB equals PAGEMSB + 1.
PCPAGE PC[14:7] Z15:Z8 Program Counter page address: Page select, for Page Erase and Page Write
PCWORD PC[6:0] Z7:Z1
Program Counter word address: Word select, for filling temporary buffer (must
be zero during Page Write operation)