ATtiny20 Atmel Corporation, ATtiny20 Datasheet - Page 23

• Manufacturer Part Number: ATtiny20
• Manufacturer: Atmel Corporation

Specifications of ATtiny20

• Flash (kbytes): 2 Kbytes
• Pin Count: 14
• Max. Operating Frequency: 12 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 5
• Hardware Qtouch Acquisition: Yes
• Max I/o Pins: 12
• Ext Interrupts: 12
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.12
• Self Program Memory: NO
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 3
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

6.5.3
8235B–AVR–04/11
OSCCAL – Oscillator Calibration Register
requirements. As the prescaler divides the master clock input to the MCU, the speed of all syn-
chronous peripherals is reduced accordingly. The division factors are given in
Table 6-4.
To avoid unintentional changes of clock frequency, a protected change sequence must be fol-
lowed to change the CLKPS bits:
At start-up, the CLKPS bits will be reset to 0b0011 to select the clock division factor of 8. The
application software must ensure that a sufficient division factor is chosen if the selected clock
source has a higher frequency than the maximum frequency of the device at the present operat-
ing conditions.
.
• Bits 7:0
The oscillator calibration register is used to trim the calibrated internal oscillator and remove pro-
cess 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
0x39
Read/Write
Initial Value
1. Write the signature for change enable of protected I/O register to register CCP
2. Within four instruction cycles, write the desired value to CLKPS bits
CLKPS3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
–
Table 20-2, “Calibration Accuracy of Internal RC Oscillator,” on page
CAL[7:0]: Oscillator Calibration Value
CAL7
Clock Prescaler Select
R/W
7
0
CLKPS2
CAL6
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
R/W
6
0
CAL5
R/W
5
0
CLKPS1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
CAL4
R/W
4
0
CAL3
R/W
3
0
CLKPS0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
CAL2
R/W
2
0
CAL1
R/W
1
0
Clock Division Factor
CAL0
R/W
0
0
8 (default)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
128
256
16
32
64
Table
1
2
4
ATtiny20
OSCCAL
174.
6-4.
23