AT43USB325 datasheet(47/109 Pages) ATMEL

47 / 109 page

3355C–USB–4/05

AT43USB325

6.4.1

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 corresponding direction control bit must be set

(one) to control the output pin. The control configuration is shown in Table 6-2.

• 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). The fol-

lowing control configuration is given:

Note:

1. X = A or B

2. In PWM mode, these bits have a different function. Refer to Table 6-6 for a detailed

description.

• Bits 3..2 – Res: Reserved Bits

These bits are reserved bits in the AT43USB325 and always read zero.

• Bits 1..0 – PWM11, PWM10: Pulse Width Modulator Select Bits 1 and 0

These bits select PWM operation of Timer/Counter1 as specified in Table 6-3.

Bit

543

$2F ($4F)

COM1A1

COM1A0

COM1B1

COM1B0

–

PWM11

PWM10

TCCR1A

Read/Write

R/W

Initial Value

Table 6-2.

Compare 1 Mode Select

(2)

COM1X1

COM1X0

Description

Timer/Counter1 disconnected from output pin OC1X.(1)

Toggle the OC1X output line.(1)

Clear the OC1X output line (to zero).(1)

Set the OC1X output line (to one).(1)

Table 6-3.

PWM Mode Select

PWM11

PWM10

Description

PWM operation of Timer/Counter1 is disabled.

Timer/Counter1 is an 8-bit PWM.

Timer/Counter1 is a 9-bit PWM.

Timer/Counter1 is a 10-bit PWM.

AT43USB325 Datasheet(PDF) 47 Page - ATMEL Corporation

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