AT90USB646 Datasheet, PDF (367/434 Pages) ATMEL Corporation – Microcontroller with 64/128K Bytes of ISP Flash and USB Controller

7593A–AVR–02/06
AT90USB64/128
Table 28-9. Read-While-Write Limit (Word Addresses)⁽¹⁾
Device
Section
AT90USB64
Read-While-Write section (RWW)
No Read-While-Write section (NRWW)
AT90USB28
Read-While-Write section (RWW)
No Read-While-Write section (NRWW)
Pages
224
32
480
32
Address
0x0000 - 0x6FFF
0x7000 - 0x7FFF
0x0000 - 0xEFFF
0xF000 - 0xFFFF
Note: 1. For details about these two section, see “NRWW – No Read-While-Write Section” on page
353 and “RWW – Read-While-Write Section” on page 353.
Table 28-10.
Explanation of different variables used in Figure 28-4 and the mapping to the Z-
pointer
Variable
Corresponding
Z-value
Description⁽¹⁾
PCMSB
16
Most significant bit in the Program Counter. (The
Program Counter is 17 bits PC[16:0])
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
Z17
Bit in Z-pointer that is mapped to PCMSB. Because
Z0 is not used, the ZPCMSB equals PCMSB + 1.
ZPAGEMSB
Bit in Z-pointer that is mapped to PCMSB. Because
Z7
Z0 is not used, the ZPAGEMSB equals PAGEMSB +
1.
PCPAGE
PC[16:7]
Z17: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)
PCMSB
15
Most significant bit in the program counter. (The program
counter is 16 bits PC[15:0])
PAGEMSB
6
Most significant bit which is used to address the words
within one page (128 words in a page requires 7 bits PC
[6:0]).
ZPCMSB
Z16
Bit in Z-register that is mapped to PCMSB. Because Z0 is
not used, the ZPCMSB equals PCMSB + 1.
ZPAGEMSB
Z7
Bit in Z-register that is mapped to PAGEMSB. Because Z0
is not used, the ZPAGEMSB equals PAGEMSB + 1.
PCPAGE
PC[15:7]
Z16: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).
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 360 for details about the use of
Z-pointer during Self-Programming.
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