ATmega16U2 Atmel Corporation, ATmega16U2 Datasheet - Page 236

• Manufacturer Part Number: ATmega16U2
• Manufacturer: Atmel Corporation

Specifications of ATmega16U2

• Flash (kbytes): 16 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 22
• Ext Interrupts: 21
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 2
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 5
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

23.8.10
23.8.11
7799D–AVR–11/10
Reading the Signature Row from Software
Preventing Flash Corruption
shown below. Refer to
High byte.
When reading the Extended Fuse byte, load 0x0002 in the Z-pointer. When an (E)LPM instruc-
tion is executed within three cycles after the BLBSET and SPMEN bits are set in the SPMCSR,
the value of the Extended Fuse byte (EFB) will be loaded in the destination register as shown
below. Refer to
Fuse byte.
Fuse and Lock bits that are programmed, will be read as zero. Fuse and Lock bits that are
unprogrammed, will be read as one.
To read the Signature Row from software, load the Z-pointer with the signature byte address
given in
LPM instruction is executed within three CPU cycles after the SIGRD and SPMEN bits are set in
SPMCSR, the signature byte value will be loaded in the destination register. The SIGRD and
SPMEN bits will auto-clear upon completion of reading the Signature Row Lock bits or if no LPM
instruction is executed within three CPU cycles. When SIGRD and SPMEN are cleared, LPM will
work as described in the Instruction set Manual
ATmega8U2/16U2/32U2 includes a unique 10 bytes serial number located in the signature row.
This unique serial number can be used as a USB serial number in the device enumeration pro-
cess. The pointer addresses to access this unique serial number are given in
page
Table 23-6.
Note:
During periods of low V
too low for the CPU and the Flash to operate properly. These issues are the same as for board
level systems using the Flash, and the same design solutions should be applied.
A Flash program corruption can be caused by two situations when the voltage is too low. First, a
regular write sequence to the Flash requires a minimum voltage to operate correctly. Secondly,
the CPU itself can execute instructions incorrectly, if the supply voltage for executing instructions
is too low.
Bit
Rd
Bit
Rd
Signature Byte
Device Signature Byte 1
Device Signature Byte 2
Device Signature Byte 3
RC Oscillator Calibration Byte
Unique Serial Number
236..
All other addresses are reserved for future use.
Table 23-6 on page 236
Signature Row Addressing
7
FHB7
7
–
Table 25-3 on page 247
Table 25-4 on page 248
6
FHB6
6
–
CC
, the Flash program can be corrupted because the supply voltage is
5
FHB5
5
–
and set the SIGRD and SPMEN bits in SPMCSR. When an
for detailed description and mapping of the Extended
4
FHB4
4
–
for detailed description and mapping of the Fuse
Z-Pointer Address
0x0000
0x0002
0x0004
0x0001
From 0x000E to 0x0018
ATmega8U2/16U2/32U2
3
FHB3
3
–
2
FHB2
2
EFB2
1
FHB1
1
EFB1
0
FHB0
0
EFB0
Table 23-6 on
236