Datasheet

227
7728G–AVR–06/10
ATtiny87/ATtiny167
Notes: 1. The default value of SUT1..0 results in maximum start-up time for the default clock source.
See Table 4-4 on page 27 for details.
2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8 MHz. See Table 4-3
on page 27 for details.
3. The CKOUT Fuse allows the system clock to be output on PORTB5. See ”Clock Output Buf-
fer” on page 31. for details.
4. See ”System Clock Prescaler” on page 37.for details.
21.2.1 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.
21.3 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.
Table 21-5. Fuse Low Byte
Fuse Low Byte Bit No Description Default Value
CKDIV8
(4)
7 Divide clock by 8 0 (programmed)
CKOUT
(3)
6 Clock output 1 (unprogrammed)
SUT1 5 Select start-up time 1 (unprogrammed)
(1)
SUT0 4 Select start-up time 0 (programmed)
(1)
CKSEL3 3 Select Clock source 0 (programmed)
(2)
CKSEL2 2 Select Clock source 0 (programmed)
(2)
CKSEL1 1 Select Clock source 1 (unprogrammed)
(2)
CKSEL0 0 Select Clock source 0 (programmed)
(2)
Table 21-6. Signature Bytes
Device Address Value Signature Byte Description
ATti ny87
0 0x1E Indicates manufactured by Atmel
1 0x93 Indicates 8 KB Flash memory
2 0x87
Indicates ATtiny87 device when address 1 contains
0x93
ATti ny16 7
0 0x1E Indicates manufactured by Atmel
1 0x94 Indicates 16 KB Flash memory
2 0x87
Indicates ATtiny167 device when address 1 contains
0x94