ATMEGA88V_14 Datasheet, PDF (130/377 Pages) ATMEL Corporation – High endurance non-volatile memory segments

ATmega48/88/168
16.11 Register description
16.11.1 TCCR1A – Timer/Counter1 control register A
Bit
7
6
5
4
3
(0x80)
COM1A1 COM1A0 COM1B1 COM1B0
–
Read/write
R/W
R/W
R/W
R/W
R
Initial value
0
0
0
0
0
2
1
0
–
WGM11 WGM10 TCCR1A
R
R/W
R/W
0
0
0
• 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 16-1 shows the COM1x1:0 bit functionality when the
WGM13:0 bits are set to a Normal or a CTC mode (non-PWM).
Table 16-1. 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)
Table 16-2 shows the COM1x1:0 bit functionality when the WGM13:0 bits are set to the fast
PWM mode.
Table 16-2. Compare output mode, fast PWM⁽¹⁾.
COM1A1/COM1B1 COM1A0/COM1B0 Description
0
0
Normal port operation, OC1A/OC1B disconnected.
WGM13:0 = 14 or 15: Toggle OC1A on compare
0
1
match, OC1B disconnected (normal port operation).
For all other WGM1 settings, normal port operation,
OC1A/OC1B disconnected.
1
0
Clear OC1A/OC1B on compare match,
set OC1A/OC1B at BOTTOM (non-inverting mode)
1
1
Set OC1A/OC1B on compare match,
clear OC1A/OC1B at BOTTOM (invertiong mode)
2545T–AVR–05/11
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