ATmega32U4 Atmel Corporation, ATmega32U4 Datasheet - Page 3

• 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

4. Protocol
4.1
7618C–AVR–07/08
Device Firmware Upgrade Introduction
These different conditions are summarized in
Figure 3-1.
Device Firmware Upgrade (DFU) is the mechanism implemented to perform device firmware
modifications. Any USB device can exploit this capability by supporting the requirements speci-
fied in this document.
Because it is unpractical for a device to concurrently perform both DFU operations and its nor-
mal run-time activities, these normal activities must cease for the duration of the DFU
operations. Doing so means that the device must change its operating mode; i.e., a printer is not
a printer while it is undergoing a firmware upgrade; it is a PROM programmer. However, a
• Boot Reset Fuse The Boot Reset Fuse (BOOTRST) can be programmed so that the Reset
• External Hardware conditions The Hardware Boot Enable fuse (HWBE) can be
Vector points to the Boot Flash section start address after reset. Once the user code is
loaded, a bootloader command (“start application”) can start executing the application code.
Note that the fuses cannot be changed by the MCU itself. This means that once the Boot
Reset Fuse is programmed, the Reset Vector will always point to the Bootloader Reset and
the fuse can only be changed through the serial or parallel programming interface. The
BOOTRST fuse is not active in the default factory configuration.
programmed so that upon special hardware conditions under reset, the bootloader execution
is forced after reset.
Boot Process
Start Bootloader
PC = boot loader section
Yes
Yes
"Software activation (jump)"
Figure 3-1 on page
BOOTRST = 0
Ext Hardware
conditions
Reset
No
No
PC = 0000h
Application
Running
3.
3