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
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