Datasheet

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.
Signature bytes can also be read by the device firmware. See section “Reading Lock, Fuse and Signature Data
from Software” on page 143.
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.
Calibration bytes can also be read by the device firmware. See section “Reading Lock, Fuse and Signature Data
from Software” on page 143.
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