ATMEGA128-16AU SL383 Atmel, ATMEGA128-16AU SL383 Datasheet - Page 133

• Manufacturer Part Number: ATMEGA128-16AU SL383
• Manufacturer: Atmel

16-bit
Timer/Counter
Register
Description
Timer/Counter1
Control Register A –
TCCR1A
Timer/Counter3
Control Register A –
TCCR3A
2467S–AVR–07/09
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•
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The COMnA1:0, COMnB1:0, and COMnC1:0 control the output compare pins (OCnA, OCnB,
and OCnC respectively) behavior. If one or both of the COMnA1:0 bits are written to one, the
OCnA output overrides the normal port functionality of the I/O pin it is connected to. If one or
both of the COMnB1:0 bits are written to one, the OCnB output overrides the normal port func-
tionality of the I/O pin it is connected to. If one or both of the COMnC1:0 bits are written to one,
the OCnC output overrides the normal port functionality of the I/O pin it is connected to. How-
ever, note that the Data Direction Register (DDR) bit corresponding to the OCnA, OCnB or
OCnC pin must be set in order to enable the output driver.
When the OCnA, OCnB or OCnC is connected to the pin, the function of the COMnx1:0 bits is
dependent of the WGMn3:0 bits setting.
the WGMn3:0 bits are set to a normal or a CTC mode (non-PWM).
Table 58. Compare Output Mode, non-PWM
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
Bit 7:6 – COMnA1:0: Compare Output Mode for Channel A
Bit 5:4 – COMnB1:0: Compare Output Mode for Channel B
Bit 3:2 – COMnC1:0: Compare Output Mode for Channel C
COMnA1/COMnB1/
COMnC1
0
0
1
1
COM1A1
COM3A1
R/W
R/W
7
0
7
0
COM1A0
COM3A0
R/W
R/W
6
0
6
0
COMnA0/COMnB0/
COM3B1
COMnC0
COM1B1
R/W
R/W
5
0
5
0
0
1
0
1
COM3B0
COM1B0
R/W
R/W
4
0
4
0
Table 58
Description
Normal port operation, OCnA/OCnB/OCnC
disconnected.
Toggle OCnA/OCnB/OCnC on compare
match.
Clear OCnA/OCnB/OCnC on compare
match (set output to low level).
Set OCnA/OCnB/OCnC on compare match
(set output to high level).
COM1C1
COM3C1
R/W
R/W
3
0
3
0
shows the COMnx1:0 bit functionality when
COM1C0
COM3C0
R/W
R/W
2
0
2
0
WGM11
WGM31
R/W
R/W
1
0
1
0
WGM10
WGM30
ATmega128
R/W
R/W
0
0
0
0
TCCR1A
TCCR3A
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