ATMEGA16U2-16AU Atmel, ATMEGA16U2-16AU Datasheet - Page 38

• Manufacturer Part Number: ATMEGA16U2-16AU
• Description: 8-bit Microcontrollers - MCU 16K Flash
• Manufacturer: Atmel

Specifications of ATMEGA16U2-16AU

• Product Category: 8-bit Microcontrollers - MCU
• Rohs: yes
• Core: AVR
• Data Bus Width: 8 bit
• Program Memory Size: 16 KB
• Data Ram Size: 1.25 KB
• Data Rom Size: 512 B
• Program Memory Type: Flash
• Factory Pack Quantity: 1250

8.11.2
8.11.3
8.11.4
7799D–AVR–11/10
CLKSEL1 – Clock Selection Register 1
CLKSTA – Clock Status Register
OSCCAL – Oscillator Calibration Register
lator is selected by the fuse bits configuration. The firmware has to check if the clock is correctly
started before selected it.
• Bit 7:4 – RCCKSEL[3:0]: CKSEL for RC oscillator
Clock configuration for the RC Oscillator. After a reset, this part of the register is loaded with the
0010b value that corresponds to the RC oscillator. Modifying this value by firmware before
switching to RC oscillator is prohibited because the RC clock will not start.
• Bit 3:0 – EXCKSEL[3:0]: CKSEL for External oscillator / Low Power Oscillator
Clock configuration for the External Oscillator / Low Power Oscillator. After a reset, if the Exter-
nal oscillator / Low Power Oscillator is selected by fuse bits, this part of the register is loaded
with the fuse configuration. Firmware can modify it to change the start-up time after the clock
switch.
• Bit 7:2 - Res: Reserved bits
These bits are reserved and will always read as zero.
• Bit 1 – RCON: RC Oscillator On
This bit is set by hardware to one if the RC Oscillator is running.
This bit is set by hardware to zero if the RC Oscillator is stoped.
• Bit 0 – EXTON: External Oscillator / Low Power Oscillator On
This bit is set by hardware to one if the External Oscillator / Low Power Oscillator is running.
This bit is set by hardware to zero if the External Oscillator / Low Power Oscillator is stoped.
• Bits 7:0 – CAL[7:0]: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to
remove process variations from the oscillator frequency. A pre-programmed calibration value is
automatically written to this register during chip reset, giving the Factory calibrated frequency as
specified in
Bit
(0xD1)
Read/Write
Initial Value
Bit
(0xD2)
Read/Write
Initial Value
Bit
(0x66)
Read/Write
Initial Value
Table 26-1 on page
RCCKSE
R/W
L3
7
0
CAL7
R/W
R
7
7
0
-
RCCKSE
R/W
L2
6
0
CAL6
R/W
R
6
6
0
-
RCCKSE
266. The application software can write this register to change
R/W
L1
CAL5
5
1
R/W
R
5
5
0
-
Device Specific Calibration Value
RCCKSE
R/W
CAL4
L0
4
0
R/W
R
4
4
0
-
EXCKSE
ATmega8U2/16U2/32U2
R/W
CAL3
L3
R/W
3
0
R
3
3
-
EXCKSE
See Bit Description
CAL2
R/W
R/W
L2
2
0
R
2
2
-
EXCKSE
RCON
CAL1
R/W
R/W
L1
R
1
1
1
0
EXCKSE
EXTON
CAL0
R/W
R/W
R
L0
0
0
0
0
OSCCAL
CLKSTA
CLKSEL1
38