ATMEGA48V_06 ATMEL [ATMEL Corporation], ATMEGA48V_06 Datasheet - Page 274

• Manufacturer Part Number: ATMEGA48V_06
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

25.7
274
Addressing the Flash During Self-Programming
ATmega48/88/168
Table 25-4.
Note:
The Z-pointer is used to address the SPM commands.
Since the Flash is organized in pages (see
be treated as having two different sections. One section, consisting of the least significant bits, is
addressing the words within a page, while the most significant bits are addressing the pages.
This is1 shown in
addressed independently. Therefore it is of major importance that the Boot Loader software
addresses the same page in both the Page Erase and Page Write operation. Once a program-
ming operation is initiated, the address is latched and the Z-pointer can be used for other
operations.
The only SPM operation that does not use the Z-pointer is Setting the Boot Loader Lock bits.
The content of the Z-pointer is ignored and will have no effect on the operation. The LPM
instruction does also use the Z-pointer to store the address. Since this instruction addresses the
Flash byte-by-byte, also the LSB (bit Z0) of the Z-pointer is used.
Bit
ZH (R31)
ZL (R30)
BOOTRST
1
0
1. “1” means unprogrammed, “0” means programmed
Boot Reset Fuse
Z15
15
Z7
7
Reset Address
Reset Vector = Application Reset (address 0x0000)
Reset Vector = Boot Loader Reset (see
Figure
Z14
Z6
14
6
25-3. Note that the Page Erase and Page Write operations are
(1)
Z13
13
Z5
5
Table 26-9 on page
Z12
Z4
12
4
Z11
11
Z3
Table 25-6 on page
3
Z10
10
Z2
2
289), the Program Counter can
281)
Z9
Z1
9
1
Z8
Z0
8
0
2545J–AVR–12/06