Datasheet

ATmega164A/PA/324A/PA/644A/PA/1284/P
 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 290
26.8.15 ATmega324A/ATmega324PA Boot Loader Parameters
In Table 26-10 through Table 26-12, 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 26-10. 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 1 256 words 4 0x0000 - 0x3EFF 0x3F00 - 0x3FFF 0x3EFF 0x3F00
1 0 512 words 8 0x0000 - 0x1DFF 0x3E00 - 0x3FFF 0x3DFF 0x3E00
0 1 1024 words 16 0x0000 - 0x1BFF 0x3C00 - 0x3FFF 0x3BFF 0x3C00
0 0 2048 words 32 0x0000 - 0x37FF 0x3800 - 0x3FFF 0x37FF 0x3800
Table 26-11. Read-While-Write limit
(1)
Section Pages Address
Read-While-Write section (RWW) 224 0x0000 - 0x37FF
No Read-While-Write section (NRWW) 32 0x3800 - 0x3FFF
Table 26-12. 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 13
Most significant bit in the Program Counter. (The Program Counter is 14 bits
PC[13:0])
PAGEMSB 5
Most significant bit which is used to address the words within one page (64
words in a page requires six bits PC [5:0]).
ZPCMSB Z14
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[13:6] Z14:Z7 Program Counter page address: Page select, for Page Erase and Page Write
PCWORD PC[5:0] Z6:Z1
Program Counter word address: Word select, for filling temporary buffer (must
be zero during Page Write operation)