
150
ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
20.3.1
Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device. This code can be read in
both serial and high-voltage programming mode, even when the device is locked.
The three signature bytes reside in a separate address space called the device signature imprint table. The signa-
ture data for ATtiny25/45/85 is given in
Table 20-7.
20.3.2
Calibration Bytes
The device signature imprint table of ATtiny25/45/85 contains two bytes of calibration data for the internal RC
Oscillator, as shown in
Table 20-6 on page 149. In normal mode of operation the calibration data for 8 MHz opera-
tion is automatically fetched and written to the OSCCAL register during reset. In ATtiny15 compatibility mode the
calibration data for 6.4 MHz operation is used instead. This procedure guarantees the internal oscillator is always
calibrated to the correct frequency.
20.4
Page Size
Table 20-7.
Device Signature Bytes
Part
Signature Byte 0
Signature Byte 1
Signature Byte 0
ATtiny25
0x1E
0x91
0x08
ATtiny45
0x1E
0x92
0x06
ATtiny85
0x1E
0x93
0x0B
Table 20-8.
No. of Words in a Page and No. of Pages in the Flash
Device
Flash Size
Page Size
PCWORD
No. of Pages
PCPAGE
PCMSB
ATtiny25
1K words
(2K bytes)
16 words
PC[3:0]
64
PC[9:4]
9
ATtiny45
2K words
(4K bytes)
32 words
PC[4:0]
64
PC[10:5]
10
ATtiny85
4K words
(8K bytes)
32 words
PC[4:0]
128
PC[11:5]
11
Table 20-9.
No. of Words in a Page and No. of Pages in the EEPROM
Device
EEPROM
Size
Page Size
PCWORD
No. of Pages
PCPAGE
EEAMSB
ATtiny25
128 bytes
4 bytes
EEA[1:0]
32
EEA[6:2]
6
ATtiny45
256 bytes
4 bytes
EEA[1:0]
64
EEA[7:2]
7
ATtiny85
512 bytes
4 bytes
EEA[1:0]
128
EEA[8:2]
8