ATMEGA328P-20PU Atmel, ATMEGA328P-20PU Datasheet - Page 279

• Manufacturer Part Number: ATMEGA328P-20PU
• Manufacturer: Atmel

Specifications of ATMEGA328P-20PU

• Cpu Family: ATmega
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 20MHz
• Interface Type: SPI/TWI/USART
• Program Memory Type: Flash
• Program Memory Size: 32KB
• Total Internal Ram Size: 2KB
• # I/os (max): 23
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• On-chip Adc: 6-chx10-bit
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Through Hole
• Pin Count: 28
• Package Type: PDIP
• Lead Free Status / Rohs Status: Compliant

26.7
26.8
8025K–AVR–10/09
Addressing the Flash During Self-Programming
Self-Programming the Flash
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.
Figure 26-3. Addressing the Flash During SPM
Note:
The program memory is updated in a page by page fashion. Before programming a page with
the data stored in the temporary page buffer, the page must be erased. The temporary page buf-
fer is filled one word at a time using SPM and the buffer can be filled either before the Page
Erase command or between a Page Erase and a Page Write operation:
Bit
ZH (R31)
ZL (R30)
Z - REGISTER
1. The different variables used in
PROGRAM MEMORY
BIT
PAGE
PROGRAM
COUNTER
15
Z15
15
Z7
7
Figure
PAGE ADDRESS
WITHIN THE FLASH
ZPCMSB
PCMSB
Z14
14
Z6
6
26-3. Note that the Page Erase and Page Write operations are
PCPAGE
Z13
13
Z5
5
Figure 26-3
ZPAGEMSB
PAGEMSB
Table 27-9 on page
PCWORD
Z12
12
Z4
4
WORD ADDRESS
WITHIN A PAGE
(1)
are listed in
1
Z11
0
0
ATmega48P/88P/168P
11
Z3
3
INSTRUCTION WORD
PAGE
Table 26-9 on page
Z10
10
Z2
2
294), the Program Counter can
Z9
Z1
9
1
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
286.
Z8
Z0
8
0
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