Datasheet
293
7674F–AVR–09/09
ATmega164P/324P/644P
24.8.16 ATmega644P Boot Loader Parameters
In Table 24-13 through Table 24-15, the parameters used in the description of the Self-Programming are given.
Note: 1. The different BOOTSZ Fuse configurations are shown in Figure 24-2 on page 282.
Note: 1. For details about these two section, see “NRWW – No Read-While-Write Section” on page 280 and “RWW –
Read-While-Write Section” on page 280.
Note: 1. Z0: should be zero for all SPM commands, byte select for the LPM instruction.
See “Addressing the Flash During Self-Programming” on page 284 for details about the use of Z-pointer during
Self-Programming.
Table 24-13. 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 - 0xFDFF 0xFE00 - 0x7FFF 0xFDFF 0xFE00
1 0 1024 words 8 0x0000 - 0xFBFF 0xFC00 - 0x7FFF 0xFBFF 0xFC00
0 1 2048 words 16 0x0000 - 0xF7FF 0xF800 - 0x7FFF 0xF7FF 0xF800
0 0 4096 words 32 0x0000 - 0xEFFF 0xF000 - 0x7FFF 0xEFFF 0xF000
Table 24-14. Read-While-Write Limit
(1)
Section Pages Address
Read-While-Write section (RWW) 224 0x0000 - 0xEFFF
No Read-While-Write section (NRWW) 32 0xF000 - 0xFFFF
Table 24-15.
Explanation of different variables used in Figure 24-3 on page 284 and the mapping to the Z-pointer
Variable
Correspondi
ng
Z-value Description
(1)
PCMSB 14
Most significant bit in the Program Counter. (The Program Counter is 15 bits
PC[14:0])
PAGEM SB 7
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 Z8
Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not used, the
ZPAGEMSB equals PAGEMSB + 1.
PCPAGE PC[14:7] Z15:Z7 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)