ATmega32U4 Atmel Corporation, ATmega32U4 Datasheet - Page 273

• 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

22.13.2
22.13.2.1
7766F–AVR–11/10
Detailed description
switch to the next bank. The RXOUTI and FIFOCON bits are then updated by hardware in accor-
dance with the status of the new bank.
RXOUTI shall always be cleared before clearing FIFOCON.
The RWAL bit always reflects the state of the current bank. This bit is set if the firmware can
read data from the bank, and cleared by hardware when the bank is empty.
The data are read by the CPU, following the next flow:
If the endpoint uses 2 banks, the second one can be filled by the HOST while the current one is
being read by the CPU. Then, when the CPU clear FIFOCON, the next bank may be already
ready and RXOUTI is set immediately.
• When the bank is filled by the host, an endpoint interrupt (EPINTx) is triggered, if enabled
• The CPU acknowledges the interrupt by clearing RXOUTI,
• The CPU can read the number of byte (N) in the current bank (N=BYCT),
• The CPU can read the data from the current bank (“N” read of UEDATX),
• The CPU can free the bank by clearing FIFOCON when all the data is read, that is:
(RXOUTE set) and RXOUTI is set. The CPU can also poll RXOUTI or FIFOCON, depending
on the software architecture,
– after “N” read of UEDATX,
– as soon as RWAL is cleared by hardware.
Example with 1 OUT data bank
RXOUTI
RXOUTI
FIFOCON
FIFOCON
Example with 2 OUT data banks
OUT
OUT
(to bank 0)
(to bank 0)
DATA
DATA
HW
HW
ACK
ACK
SW
SW
read data from CPU
OUT
BANK 0
NAK
read data from CPU
BANK 0
(to bank 1)
DATA
SW
OUT
ACK
(to bank 0)
DATA
HW
ATmega16/32U4
SW
HW
ACK
SW
read data from CPU
BANK 1
SW
read data from CPU
BANK 0
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