ATtiny20 Atmel Corporation, ATtiny20 Datasheet - Page 67

• 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

8235B–AVR–04/11
operating frequency of the fast PWM mode can be twice as high as the phase correct PWM
mode that use dual-slope operation. This high frequency makes the fast PWM mode well suited
for power regulation, rectification, and DAC applications. High frequency allows physically small
sized external components (coils, capacitors), and therefore reduces total system cost.
In fast PWM mode, the counter is incremented until the counter value matches the TOP value.
The counter is then cleared at the following timer clock cycle. The timing diagram for the fast
PWM mode is shown in
shown as a histogram for illustrating the single-slope operation. The diagram includes non-
inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes repre-
sent Compare Matches between OCR0x and TCNT0.
Figure 11-6. Fast PWM Mode, Timing Diagram
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches TOP. If the inter-
rupt is enabled, the interrupt handler routine can be used for updating the compare value.
In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC0x pins.
Setting the COM0x[1:0] bits to two will produce a non-inverted PWM and an inverted PWM out-
put can be generated by setting the COM0x[1:0] to three: Setting the COM0A[1:0] bits to one
allowes the OC0A pin to toggle on Compare Matches if the WGM02 bit is set. This option is not
available for the OC0B pin (See
ible on the port pin if the data direction for the port pin is set as output. The PWM waveform is
generated by setting (or clearing) the OC0x Register at the Compare Match between OCR0x
and TCNT0, and clearing (or setting) the OC0x Register at the timer clock cycle the counter is
cleared (changes from TOP to BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
The extreme values for the OCR0x Register represents special cases when generating a PWM
waveform output in the fast PWM mode. If OCR0x is set equal to BOTTOM, the output will be a
TCNTn
OCnx
OCnx
Period
1
2
Figure 11-6 on page
3
Table 11-3 on page
f
OCnxPWM
4
=
67. The TCNT0 value is in the timing diagram
---------------------------------- -
N
5
⋅
(
f
clk_I/O
TOP
72). The actual OC0x value will only be vis-
6
+
1
)
7
OCRnx Interrupt Flag Set
OCRnx Update and
TOVn Interrupt Flag Set
(COMnx[1:0] = 2)
(COMnx[1:0] = 3)
ATtiny20
67