ATTINY461-20SUR Atmel, ATTINY461-20SUR Datasheet - Page 94

• Manufacturer Part Number: ATTINY461-20SUR
• Description: MCU AVR 4KB FLASH 20MHZ 20SOIC
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY461-20SUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 16
• Program Memory Size: 4KB (2K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 11x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

12.4.1
12.5
94
Output Compare Unit
ATtiny261/461/861
Counter Initialization for Asynchronous Mode
To set Timer/Counter1 to asynchronous mode follow the procedure below:
The comparator continuously compares TCNT1 with the Output Compare Registers (OCR1A,
OCR1B, OCR1C and OCR1D). Whenever TCNT1 equals to the Output Compare Register, the
comparator signals a match. A match will set the Output Compare Flag (OCF1A, OCF1B or
OCF1D) at the next timer clock cycle. If the corresponding interrupt is enabled, the Output Com-
pare Flag generates an Output Compare interrupt. The Output Compare Flag is automatically
cleared when the interrupt is executed. Alternatively, the flag can be cleared by software by writ-
ing a logical one to its I/O bit location. The Waveform Generator uses the match signal to
generate an output according to operating mode set by bits PWM1A, PWM1B, WGM11:10 and
COM1x1:0. The top and bottom signals are used by the Waveform Generator for handling the
special cases of the extreme values in some modes of operation
page
Figure 12-5. Output Compare Unit, Block Diagram
The OCR1x Registers are double buffered when using any of the Pulse Width Modulation
(PWM) modes. For the normal mode of operation, the double buffering is disabled. The double
buffering synchronizes the update of the OCR1x Compare Registers to either top or bottom of
the counting sequence. The synchronization prevents the occurrence of odd-length, non-sym-
1. Enable PLL.
2. Wait 100 µs for PLL to stabilize.
3. Poll the PLOCK bit until it is set.
4. Set the PCKE bit in the PLLCSR register which enables the asynchronous mode.
99.).
Figure 12-5
BOTTOM
FOCn
OCRnx
TOP
shows a block diagram of the Output Compare unit.
10-BIT OCRnx
Waveform Generator
=
8-BIT DATA BUS
(10-bit Comparator )
OCWnx
TCnH
10-BIT TCNTn
(See “Modes of Operation” on
TCNTn
COMnX1:0
PWMnx
WGM10
OCFnx (Int.Req.)
2588E–AVR–08/10