ATmega32U4 Atmel Corporation, ATmega32U4 Datasheet - Page 33

• 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

6.5.2
6.6
7766F–AVR–11/10
External Clock
Oscillator Control Register – RCCTRL
The temperature sensitivity is quite linear but as said previously depends on the process. To
determine its slope, the frequency must be measured at two temperatures. The temperature
sensor of the ATmega16U4/ATmega32U4 allows such an operation, that is detailed on
24.6.1 ”Sensor Calibration” on page
in function of the temperature measured.
Note that this oscillator is used to time EEPROM and Flash write accesses, and these write
times will be affected accordingly. If the EEPROM or Flash are written, do not calibrate to more
than 8.8 MHz. Otherwise, the EEPROM or Flash write may fail.
Bits 7..1 – Reserved
Do not set these bits. Bits should be read as ‘0’.
Bit 0– RCFREQ: RC Oscillator Frequency Select
When this bit is cleared (default value), the RC Oscillator output frequency is set to 8 MHz.
When the bit is set, the RC output frequency is 1 MHz. Note that the OSCCAL value has the
same effect on both 8 MHz and 1 MHz output modes (~0.4% / step).
The device can utilize a external clock source as shown in
external clock, the CKSEL Fuses must be programmed as shown in
Figure 6-3.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Bit
Read/Write
Initial Value
6-9.
7
-
R
0
External Clock Drive Configuration
6
-
R
0
EXTERNAL
SIGNAL
CLOCK
5
-
R
0
NC
300. It is then possible to calibrate the oscillator frequency
4
-
R
0
3
-
R
0
XTAL2
XTAL1
GND
2
-
R
0
Figure
1
-
R
0
ATmega16/32U4
6-3. To run the device on an
Table
0
RCFREQ
R/W
0
6-1.
RCCTRL
Section
33