Datasheet

154
2586N–AVR–04/11
ATtiny25/45/85
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 147.
The three signature bytes reside in a separate address space called the device signature imprint
table. The signature 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 153. In normal mode of operation the
calibration data for 8 MHz operation 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 147.
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
ATti ny2 5
1K words
(2K bytes)
16 words PC[3:0] 64 PC[9:4] 9
ATti ny4 5
2K words
(4K bytes)
32 words PC[4:0] 64 PC[10:5] 10
ATti ny8 5
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