Rainbow Electronics ATmega128RFA1 - Manual (Page 269)

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8266A-MCU Wireless-12/09
ATmega128RFA1
Combined with the WGM11:0 bits found in the TCCR1A Register, these bits control the
counting sequence of the counter, the source for maximum (TOP) counter value, and
what type of waveform generation to be used. Modes of operation supported by the
Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare match (CTC)
mode, and three types of Pulse Width Modulation (PWM) modes. For more information
on the different modes see section "Modes of Operation".
Table 18-10 WGM1 Register Bits
Register Bits Value Description
0x0 Normal mode of operation
0x1 PWM, phase correct, 8-bit
0x2 PWM, phase correct, 9-bit
0x3 PWM, phase correct, 10-bit
0x4 CTC, TOP = OCRnA
0x5 Fast PWM, 8-bit
0x6 Fast PWM, 9-bit
0x7 Fast PWM, 10-bit
0x8 PWM, Phase and frequency correct, TOP =
ICRn
0x9 PWM, Phase and frequency correct, TOP =
OCRnA
0xA PWM, Phase correct, TOP = ICRn
0xB PWM, Phase correct, TOP = OCRnA
0xC CTC, TOP = OCRnA
0xD Reserved
0xE Fast PWM, TOP = ICRn
WGM11:10
0xF Fast PWM, TOP = OCRnA
• Bit 2:0 – CS12:10 - Clock Select
The three clock select bits select the clock source to be used by the Timer/Counter1
according to the following table. If external pin modes are used for the Timer/Counter1,
transitions on the T1 pin will clock the counter even if the pin is configured as an output.
This feature allows software control of the counting.
Table 18-11 CS1 Register Bits
Register Bits Value Description
0x00 No clock source (Timer/Counter stopped)
0x01 clk_IO/1 (no prescaling)
0x02 clk_IO/8 (from prescaler)
0x03 clk_IO/64 (from prescaler)
0x04 clk_IO/256 (from prescaler)
0x05 clk_IO/1024 (from prescaler)
0x06 External clock source on Tn pin, clock on
falling edge
CS12:10
0x07 External clock source on Tn pin, clock on
rising edge