ATmega32U4 Atmel Corporation, ATmega32U4 Datasheet - Page 267

• Manufacturer Part Number: ATmega32U4
• Manufacturer: Atmel Corporation

Specifications of ATmega32U4

• Flash (kbytes): 32 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 14
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 26
• Ext Interrupts: 13
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 12
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 3.3
• Eeprom (bytes): 1024
• 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: 4
• Output Compare Channels: 12
• Input Capture Channels: 2
• Pwm Channels: 8
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

22.4
22.5
22.6
7766F–AVR–11/10
USB reset
Endpoint selection
Endpoint activation
The data toggle field remains unchanged.
The other registers remain unchanged.
The endpoint configuration remains active and the endpoint is still enabled.
The endpoint reset may be associated with a clear of the data toggle command (RSTDT bit) as
an answer to the CLEAR_FEATURE USB command.
When an USB reset is detected on the USB line (SE0 state with a minimum duration of 2.5µs),
the next operations are performed by the controller:
If the CPU hardware reset function is activated (RSTCPU bit set in UDCON register), a reset is
generated to the CPU core without disabling the USB controller (that follows the same behavior
than after a standard USB End of Reset, and remains attached). That feature may be used to
enhance device reliability.
Prior to any operation performed by the CPU, the endpoint must first be selected. This is done
by setting the EPNUM2:0 bits (UENUM register) with the endpoint number which will be man-
aged by the CPU.
The CPU can then access to the various endpoint registers and data.
The endpoint is maintained under reset as long as the EPEN bit is not set.
The following flow must be respected in order to activate an endpoint:
• the UEINTX, UESTA0X and UESTA1X are restored to their reset value.
• all the endpoints are disabled
• the default control endpoint remains configured (see Section 22.3, page 266 for more
details).
ATmega16/32U4
267