ATMEGA161 datasheet(46/134 Pages) ATMEL

46 / 134 page

ATmega161(L)

The Timer/Counter1 supports two Output Compare functions using the Output Compare Register 1 A and B – OCR1A and

OCR1B as the data sources to be compared to the Timer/Counter1 contents. The Output Compare functions include

optional clearing of the counter on compareA match, and actions on the Output Compare pins on both compare matches.

Timer/Counter1 can also be used as a 8-, 9- or 10-bit Pulse With Modulator. In this mode the counter and the

OCR1A/OCR1B registers serve as a dual glitch-free stand-alone PWM with centered pulses. Alternatively, the

Timer/Counter1 can be configured to operate at twice the speed in PWM mode, but without centered pulses. Refer to

page 50 for a detailed description on this function.

The Input Capture function of Timer/Counter1 provides a capture of the Timer/Counter1 contents to the Input Capture

defined by the Timer/Counter1 Control Register – TCCR1B. In addition, the Analog Comparator can be set to trigger the

Input Capture. Refer to the section, “The Analog Comparator”, for details on this. The ICP pin logic is shown in Figure 37.

Figure 37. ICP Pin Schematic Diagram

If the noise canceler function is enabled, the actual trigger condition for the capture event is monitored over 4 samples, and

all 4 must be equal to activate the capture flag.

Timer/Counter1 Control Register A – TCCR1A

• Bits 7,6 - COM1A1, COM1A0: Compare Output Mode1A, bits 1 and 0

The COM1A1 and COM1A0 control bits determine any output pin action following a compare match in Timer/Counter1.

Any output pin actions affect pin OC1A – Output CompareA pin 1. This is an alternative function to an I/O port, and the cor-

responding direction control bit must be set (one) to control an output pin. The control configuration is shown in Table 14.

• Bits 5,4 - COM1B1, COM1B0: Compare Output Mode1B, bits 1 and 0

The COM1B1 and COM1B0 control bits determine any output pin action following a compare match in Timer/Counter1.

Any output pin actions affect pin OC1B – Output CompareB. This is an alternative function to an I/O port, and the corre-

sponding direction control bit must be set (one) to control an output pin. The following control configuration is given:

X = A or B

In PWM mode, these bits have a different function. Refer to Table 18 for a detailed description.

Bit

$2F ($4F)

COM1A1

COM1A0

COM1B1

COM1B0

FOC1A

FOC1B

PWM11

PWM10

TCCR1A

Read/Write

R/W

R/w

R/W

Initial value

Table 14. Compare 1 Mode Select

COM1X1

COM1X0

Description

Timer/Counter1 disconnected from output pin OC1X

Toggle the OC1X output line.

Clear the OC1X output line (to zero).

Set the OC1X output line (to one).

ATMEGA161 Datasheet(PDF) 46 Page - ATMEL Corporation

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