ATmega328P datasheet(289/345 Pages) ATMEL

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289

7810A–AVR–11/09

ATmega328P [Preliminary]

Note:

1. The default value of SUT1..0 results in maximum start-up time for the default clock source.

See Table 8-11 on page 32 for details.

2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8 MHz. See Table 8-10 on

page 32 for details.

3. The CKOUT Fuse allows the system clock to be output on PORTB0. See “Clock Output Buffer”

on page 34 for details.

4. See “System Clock Prescaler” on page 34 for details.

The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are locked if

Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the Lock bits.

27.2.1

Latching of Fuses

The fuse values are latched when the device enters programming mode and changes of the

fuse values will have no effect until the part leaves Programming mode. This does not apply to

the EESAVE Fuse which will take effect once it is programmed. The fuses are also latched on

Power-up in Normal mode.

27.3

Signature Bytes

All Atmel microcontrollers have a three-byte signature code which identifies the device. This

code can be read in both serial and parallel mode, also when the device is locked. The three

bytes reside in a separate address space. For the ATmega328P the signature bytes are given in

Table 27-8.

27.4

Calibration Byte

The ATmega328P has a byte calibration value for the Internal RC Oscillator. This byte resides in

the high byte of address 0x000 in the signature address space. During reset, this byte is auto-

matically written into the OSCCAL Register to ensure correct frequency of the calibrated RC

Oscillator.

Table 27-7.

Fuse Low Byte

Low Fuse Byte

Bit No

Description

Default Value

CKDIV8(4)

Divide clock by 8

0 (programmed)

CKOUT(3)

Clock output

1 (unprogrammed)

SUT1

Select start-up time

1 (unprogrammed)(1)

SUT0

Select start-up time

0 (programmed)(1)

CKSEL3

Select Clock source

0 (programmed)(2)

CKSEL2

Select Clock source

0 (programmed)(2)

CKSEL1

Select Clock source

1 (unprogrammed)(2)

CKSEL0

Select Clock source

0 (programmed)(2)

Table 27-8.

Device ID

Part

Signature Bytes Address

0x000

0x001

0x002

ATmega328P

0x1E

0x95

0x0F

ATmega328P Datasheet(PDF) 289 Page - ATMEL Corporation

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