ATMEGA8U2-AU Atmel, ATMEGA8U2-AU Datasheet - Page 94
ATMEGA8U2-AU
Manufacturer Part Number
ATMEGA8U2-AU
Description
MCU AVR 8K FLASH 16MHZ 32TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA8U2-AU
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
Processor Series
ATmega
Core
AVR
Data Bus Width
8 bit
Data Ram Size
512 B
Interface Type
SPI, USART, USB
Maximum Clock Frequency
16 MHz
Number Of Programmable I/os
22
Number Of Timers
2
Operating Supply Voltage
5 V
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
3rd Party Development Tools
EWAVR, EWAVR-BL
Development Tools By Supplier
ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT, AT90USBKEY, ATEVK525
Minimum Operating Temperature
- 40 C
Operating Temperature Range
- 40 C to + 85 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Data Converters
-
Lead Free Status / Rohs Status
Details
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
ATMEGA8U2-AU
Manufacturer:
Atmel
Quantity:
2 772
Part Number:
ATMEGA8U2-AU
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
- Current page: 94 of 309
- Download datasheet (6Mb)
15.5.1
15.5.2
15.5.3
7799D–AVR–11/10
Force Output Compare
Compare Match Blocking by TCNT0 Write
Using the Output Compare Unit
Figure 15-3. Output Compare Unit, Block Diagram
The OCR0x Registers are double buffered when using any of the Pulse Width Modulation
(PWM) modes. For the normal and Clear Timer on Compare (CTC) modes of operation, the dou-
ble buffering is disabled. The double buffering synchronizes the update of the OCR0x Compare
Registers to either top or bottom of the counting sequence. The synchronization prevents the
occurrence of odd-length, non-symmetrical PWM pulses, thereby making the output glitch-free.
The OCR0x Register access may seem complex, but this is not case. When the double buffering
is enabled, the CPU has access to the OCR0x Buffer Register, and if double buffering is dis-
abled the CPU will access the OCR0x directly.
In non-PWM waveform generation modes, the match output of the comparator can be forced by
writing a one to the Force Output Compare (FOC0x) bit. Forcing Compare Match will not set the
OCF0x Flag or reload/clear the timer, but the OC0x pin will be updated as if a real Compare
Match had occurred (the COM0x1:0 bits settings define whether the OC0x pin is set, cleared or
toggled).
All CPU write operations to the TCNT0 Register will block any Compare Match that occur in the
next timer clock cycle, even when the timer is stopped. This feature allows OCR0x to be initial-
ized to the same value as TCNT0 without triggering an interrupt when the Timer/Counter clock is
enabled.
Since writing TCNT0 in any mode of operation will block all Compare Matches for one timer
clock cycle, there are risks involved when changing TCNT0 when using the Output Compare
Unit, independently of whether the Timer/Counter is running or not. If the value written to TCNT0
equals the OCR0x value, the Compare Match will be missed, resulting in incorrect waveform
bottom
FOCn
top
OCRnx
Waveform Generator
WGMn1:0
=
(8-bit Comparator )
DATA BUS
COMnX1:0
ATmega8U2/16U2/32U2
TCNTn
OCFnx (Int.Req.)
OCnx
94
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