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.
Table 25-6. Device and JTAG ID
Signature Bytes Address
JTAG
Part
0x000
0x001
0x93
0x94
0x95
0x002
Part Number
9389
Manufacture ID
0x1F
ATmega8U2
ATmega16U2
ATmega32U2
0x1E
0x1E
0x1E
0x89
0x89
0x8A
9489
0x1F
958A
0x1F
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 25-7. No. of Words in a Page and No. of Pages in the Flash
No. of
Pages
Device
ATmega8U2
ATmega16U2
ATmega32U2
Flash Size
4K words (8Kbytes)
8K words (16Kbytes)
16K words (32Kbytes)
Page Size
32 words
64 words
64 words
PCWORD
PC[4:0]
PC[5:0]
PC[5:0]
PCPAGE
PC[11:6]
PC[12:6]
PC[13:6]
PCMSB
11
128
128
256
12
13
Table 25-8. No. of Bytes in a Page and No. of Pages in the EEPROM
No. of
Pages
Device
ATmega8U2
ATmega16U2
ATmega32U2
EEPROM Size
256 bytes
Page Size
4 bytes
PCWORD
EEA[1:0]
EEA[1:0]
EEA[1:0]
PCPAGE
EEA[8:2]
EEA[8:2]
EEA[9:2]
EEAMSB
128
128
256
8
8
9
512 bytes
4 bytes
1K bytes
4 bytes
249
7799D–AVR–11/10
ATMEL [ ATMEL ]
