ATmega32A datasheet(268/352 Pages) ATMEL

268 / 352 page

268

8155B–AVR–07/09

ATmega32A

Notes:

1. The default value of SUT1:0 results in maximum start-up time. SeeTable 8-9 on page 30 for

details.

2. The default setting of CKSEL3:0 results in internal RC Oscillator @ 1MHz. See Table 8-1 on

page 26 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.

26.2.1

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.

26.3

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 ATmega32A the signature bytes are:

$000: $1E (indicates manufactured by Atmel)

$001: $95 (indicates 32KB Flash memory)

$002: $02 (indicates ATmega32A device when $001 is $95)

26.4

Calibration Byte

The ATmega32A stores four different calibration values for the internal RC Oscillator. These

bytes resides in the signature row High Byte of the addresses 0x0000, 0x0001, 0x0002, and

0x0003 for 1, 2, 4, and 8 Mhz respectively. During Reset, the 1 MHz value is automatically

loaded into the OSCCAL Register. If other frequencies are used, the calibration value has to be

loaded manually, see “OSCCAL – Oscillator Calibration Register” on page 32 for details.

Table 26-4.

Fuse Low Byte

Fuse Low

Byte

Bit No.

Description

Default Value

BODLEVEL

Brown-out Detector trigger level

1 (unprogrammed)

BODEN

Brown-out Detector enable

1 (unprogrammed, BOD disabled)

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

0 (programmed)(2)

CKSEL0

Select Clock source

1 (unprogrammed)(2)

ATmega32A Datasheet(PDF) 268 Page - ATMEL Corporation

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