ATtiny261 Atmel Corporation, ATtiny261 Datasheet - Page 25

• 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

6.1.3
6.1.4
6.1.5
6.1.6
6.2
2588E–AVR–08/10
Clock Sources
Flash Clock – clk
ADC Clock – clk
Fast Peripheral Clock – clk
PLL System Clock – clk
The Flash clock controls operation of the Flash interface. The Flash clock is usually active simul-
taneously with the CPU clock.
The ADC is provided with a dedicated clock domain. This allows halting the CPU and I/O clocks
in order to reduce noise generated by digital circuitry. This gives more accurate ADC conversion
results.
Selected peripherals can be clocked at a frequency higher than the CPU core. The fast periph-
eral clock is generated by an on-chip PLL circuit.
The PLL can also be used to generate a system clock. The clock signal can be prescaled to
avoid overclocking the CPU.
The device has the following clock source options, selectable by Flash Fuse bits as shown
below. The clock from the selected source is input to the AVR clock generator, and routed to the
appropriate modules.
Table 6-1.
Note:
The various choices for each clocking option is given in the following sections. When the CPU
wakes up from Power-down or Power-save, the selected clock source is used to time the start-
up, ensuring stable oscillator operation before instruction execution starts. When the CPU starts
from reset, there is an additional delay allowing the power to reach a stable level before com-
ADC
Device Clocking Option
External Clock (see
High-Frequency PLL Clock (see
Calibrated Internal 8 MHz Oscillator (see
Internal 128 kHz Oscillator (see
Low-Frequency Crystal Oscillator (see
Crystal Oscillator / Ceramic Resonator
0.4...0.9 MHz (see
Crystal Oscillator / Ceramic Resonator
0.9...3.0 MHz (see
Crystal Oscillator / Ceramic Resonator
3...8 MHz (see
Crystal Oscillator / Ceramic Resonator
8...20 MHz (see
FLASH
1. For all fuses “1” means unprogrammed and “0” means programmed.
ADC
PCK
Device Clocking Options Select
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(1)
vs. PB4 and PB5 Functionality
CKSEL3:0
0000
0001
0010
0011
1000
1001
1010
1011
1100
1101
01xx
1110
1111
XTAL1
XTAL1
XTAL1
XTAL1
XTAL1
XTAL1
PB4
I/O
I/O
I/O
XTAL2
XTAL2
XTAL2
XTAL2
XTAL2
PB5
I/O
I/O
I/O
I/O
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