ATtiny48 datasheet(186/266 Pages) ATMEL

186 / 266 page

186

8008C–AVR–03/09

ATtiny48/88

Note:

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

See Table 6-4 on page 28 for details.

2. The default setting of CKSEL1..0 results in internal oscillator @ 8 MHz. See Table 6-3 on page

28 for details.

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

on page 30 for details.

4. See “System Clock Prescaler” on page 30 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.

20.2.1

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.

20.3

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 ATtiny48/88 the signature bytes are given in

Table 20-6.

20.4

Calibration Byte

The ATtiny48/88 has a byte calibration value for the internal oscillator. This byte resides in the

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

cally written into the OSCCAL Register to ensure correct frequency of the calibrated oscillator.

Table 20-5.

Fuse Low 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)

1 (unprogrammed)(2)

CKSEL1

Select Clock source

1 (unprogrammed)(2)

CKSEL0

Select Clock source

0 (programmed)(2)

Table 20-6.

Device ID

Part

Signature Bytes Address

0x000

0x001

0x002

ATtiny48

0x1E

0x92

0x09

ATtiny88

0x1E

0x93

0x11

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