ATtiny261 Atmel Corporation, ATtiny261 Datasheet - Page 26

• Manufacturer Part Number: ATtiny261
• Manufacturer: Atmel Corporation

Specifications of ATtiny261

• Flash (kbytes): 2 Kbytes
• Pin Count: 20
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 4
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 16
• Ext Interrupts: 16
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• 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
• Eeprom (bytes): 128
• Self Program Memory: YES
• 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: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

6.2.1
6.2.2
26
ATtiny261/461/861
External Clock
High-Frequency PLL Clock
mencing normal operation. The watchdog oscillator is used for timing this real-time part of the
start-up time. The number of WD oscillator cycles used for each time-out is shown in
Table 6-2.
To drive the device from an external clock source, CLKI should be driven as shown in
2. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”.
Figure 6-2.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 6-3.
When applying an external clock, it is required to avoid sudden changes in the applied clock fre-
quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from
one clock cycle to the next can lead to unpredictable behavior. It is required to ensure that the
MCU is kept in Reset during such changes in the clock frequency.
Note that the system clock prescaler can be used to implement run-time changes of the internal
clock frequency. See
The internal PLL generates a clock signal with a frequency eight times higher than the source
input. The PLL uses the output of the internal 8 MHz oscillator as source and the default setting
generates a fast peripheral clock signal of 64 MHz.
SUT1:0
00
01
10
11
6-3.
Typ Time-out
Start-up Time from Power-
Number of Watchdog Oscillator Cycles
External Clock Drive Configuration
Start-up Times for the External Clock Selection
EXTERNAL
down and Power-save
64 ms
4 ms
SIGNAL
CLOCK
“System Clock Prescaler” on page 31
6 CK
6 CK
6 CK
Additional Delay from
Reserved
14CK + 64 ms
14CK + 4 ms
Reset
14CK
CLKI
GND
for details.
Number of Cycles
8K (8,192)
512
BOD enabled
Fast rising power
Slowly rising power
Recommended Usage
2588E–AVR–08/10
Table
Figure 6-
6-2.