Datasheet

2466T–AVR–07/10

ATmega16(L)

16-bit

Timer/Counter

Description

Timer/Counter1

Control Register A –

TCCR1A

• Bit 7:6 – COM1A1:0: Compare Output Mode for Channel A

• Bit 5:4 – COM1B1:0: Compare Output Mode for Channel B

The COM1A1:0 and COM1B1:0 control the Output Compare pins (OC1A and OC1B respec-

tively) behavior. If one or both of the COM1A1:0 bits are written to one, the OC1A output

overrides the normal port functionality of the I/O pin it is connected to. If one or both of the

COM1B1:0 bit are written to one, the OC1B output overrides the normal port functionality of the

I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit correspond-

ing to the OC1A or OC1B pin must be set in order to enable the output driver.

When the OC1A or OC1B is connected to the pin, the function of the COM1x1:0 bits is depen-

dent of the WGM13:0 bits setting. Table 44 shows the COM1x1:0 bit functionality when the

WGM13:0 bits are set to a normal or a CTC mode (non-PWM).

Table 45 shows the COM1x1:0 bit functionality when the WGM13:0 bits are set to the fast PWM

mode.

Bit 76543210

COM1A1 COM1A0 COM1B1 COM1B0 FOC1A FOC1B WGM11 WGM10 TCCR1A

Read/Write R/W R/W R/W R/W W W R/W R/W

Initial Value00000000

Table 44. Compare Output Mode, non-PWM

COM1A1/COM1B1 COM1A0/COM1B0 Description

0 0 Normal port operation, OC1A/OC1B

disconnected.

0 1 Toggle OC1A/OC1B on compare match

1 0 Clear OC1A/OC1B on compare match (Set

output to low level)

1 1 Set OC1A/OC1B on compare match (Set

output to high level)