Datasheet

249
7799D–AVR–11/10
ATmega8U2/16U2/32U2
25.2.1 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.
25.3 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 ATmega8U2/16U2/32U2 the signature bytes
are given in Table 25-6.
25.4 Calibration Byte
The ATmega8U2/16U2/32U2 has a byte calibration value for the internal RC Oscillator. This
byte resides in the high byte of address 0x000 in the signature address space. During reset, this
byte is automatically written into the OSCCAL Register to ensure correct frequency of the cali-
brated RC Oscillator.
25.5 Page Size
Table 25-6. Device and JTAG ID
Part
Signature Bytes Address JTAG
0x000 0x001 0x002 Part Number Manufacture ID
ATmega8U2 0x1E 0x93 0x89 9389 0x1F
ATmega16U2 0x1E 0x94 0x89 9489 0x1F
ATmega32U2 0x1E 0x95 0x8A 958A 0x1F
Table 25-7. No. of Words in a Page and No. of Pages in the Flash
Device Flash Size Page Size PCWORD
No. of
Pages PCPAGE PCMSB
ATmega8U2 4K words (8Kbytes) 32 words PC[4:0] 128 PC[11:6] 11
ATmega16U2 8K words (16Kbytes) 64 words PC[5:0] 128 PC[12:6] 12
ATmega32U2 16K words (32Kbytes) 64 words PC[5:0] 256 PC[13:6] 13
Table 25-8. No. of Bytes in a Page and No. of Pages in the EEPROM
Device EEPROM Size Page Size PCWORD
No. of
Pages PCPAGE EEAMSB
ATmega8U2 256 bytes 4 bytes EEA[1:0] 128 EEA[8:2] 8
ATmega16U2 512 bytes 4 bytes EEA[1:0] 128 EEA[8:2] 8
ATmega32U2 1K bytes 4 bytes EEA[1:0] 256 EEA[9:2] 9