ATtiny44 datasheet(161/236 Pages) ATMEL

161 / 236 page

161

8006H–AVR–10/09

ATtiny24/44/84

Notes:

1. See “System Clock Prescaler” on page 30 for details.

2. Allows system clock to be output on pin. See “Clock Output Buffer” on page 30 for details.

3. The default value results in maximum start-up time for the default clock source. See Table 6-5

on page 27 for details.

4. The default setting results in internal RC Oscillator @ 8.0 MHz. See Table 6-4 on page 27 for

details.

Note that fuse bits are locked if Lock Bit 1 (LB1) is programmed. Fuse bits should be pro-

grammed before lock bits. The status of fuse bits is not affected by chip erase.

Fuse bits can also be read by device firmware. See section “Reading Lock, Fuse and Signature

Data from Software” on page 155.

19.2.1

Latching of Fuses

Fuse values are latched when the device enters programming mode and changes to fuse values

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. Fuses are also latched on power-up.

19.3

Device Signature Imprint Table

The device signature imprint table is a dedicated memory area used for storing miscellaneous

device information, such as the device signature and oscillator calibaration data. Most of this

memory segment is reserved for internal use, as outlined in Table 19-6.

Notes:

1. See section “Signature Bytes” for more information.

2. See section “Calibration Byte” for more information.

Table 19-5.

Fuse Low Byte

Bit No

Description

Default Value

CKDIV8 (1)

Divide clock by 8

0 (programmed)

CKOUT (2)

Clock Output Enable

1 (unprogrammed)

SUT1 (3)

Select start-up time

1 (unprogrammed)

SUT0 (3)

Select start-up time

0 (programmed)

CKSEL3 (4)

Select Clock source

0 (programmed)

CKSEL2 (4)

Select Clock source

0 (programmed)

CKSEL1 (4)

Select Clock source

1 (unprogrammed)

CKSEL0 (4)

Select Clock source

0 (programmed)

Table 19-6.

Contents of Device Signature Imprint Table.

Address

High Byte

0x00

Signature byte 0 (1)

0x01

Calibration data for internal oscillator (2)

0x02

Signature byte 1 (1)

0x03

Reserved for internal use

0x04

Signature byte 2 (1)

0x05 ... 0x2A

Reserved for internal use

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