ATMEGA8U2-AUR Atmel, ATMEGA8U2-AUR Datasheet - Page 29

• Manufacturer Part Number: ATMEGA8U2-AUR
• Description: MCU AVR 8K FLASH 16MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8U2-AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Converters: -

8.3
8.3.1
8.3.2
7799D–AVR–11/10
Clock Sources
Default Clock Source
Clock Startup Sequence
The device has the following clock source options, selectable by Flash Fuse bits as shown
below. The clock from the selected source is input to the AVR clock generator, and routed to the
appropriate modules.
Table 8-1.
Note:
The device is shipped with internal RC oscillator at 8.0 MHz and with the fuse CKDIV8 pro-
grammed, resulting in 1.0 MHz system clock. The startup time is set to maximum and time-out
period enabled. (CKSEL = "0010", SUT = "10", CKDIV8 = "0"). The default setting ensures that
all users can make their desired clock source setting using any available programming interface.
Any clock source needs a sufficient V
cycles before it can be considered stable.
To ensure sufficient V
the device reset is released by all other reset sources.
describes the start conditions for the internal reset. The delay (t
Oscillator and the number of cycles in the delay is set by the SUTx and CKSELx fuse bits. The
selectable delays are shown in
dependent as shown in
Table 8-2.
Main purpose of the delay is to keep the AVR in reset until it is supplied with minimum Vcc. The
delay will not monitor the actual voltage and it will be required to select a delay longer than the
Vcc rise time. If this is not possible, an internal or external Brown-Out Detection circuit should be
used. A BOD circuit will ensure sufficient Vcc before it releases the reset, and the time-out delay
can be disabled. Disabling the time-out delay without utilizing a Brown-Out Detection circuit is
not recommended.
Device Clocking Option
Low Power Crystal Oscillator
Full Swing Crystal Oscillator
Reserved
Reserved
Calibrated Internal RC Oscillator
External Clock
Reserved
Typ Time-out (V
1. For all fuses “1” means unprogrammed while “0” means programmed.
4.1 ms
65 ms
0 ms
Device Clocking Options Select
Number of Watchdog Oscillator Cycles
CC
= 5.0V)
CC
“Typical Characteristics” on page
, the device issues an internal reset with a time-out delay (t
Table
CC
Typ Time-out (V
8-2. The frequency of the Watchdog Oscillator is voltage
to start oscillating and a minimum number of oscillating
(1)
4.3 ms
69 ms
0 ms
ATmega8U2/16U2/32U2
CC
= 3.0V)
“On-chip Debug System” on page 45
273.
TOUT
) is timed from the Watchdog
Number of Cycles
8K (8,192)
0101 - 0100
1111 - 1000
0111 - 0110
CKSEL3:0
512
0011
0010
0000
0001
0
TOUT
) after
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