ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 130

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Register Description
TCCR0A – Timer/Counter
Control Register A
130
ATmega640/1280/1281/2560/2561
• Bits 7:6 – COM0A1:0: Compare Match Output A Mode
These bits control the Output Compare pin (OC0A) behavior. If one or both of the
COM0A1:0 bits are set, the OC0A output overrides the normal port functionality of the
I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit cor-
responding to the OC0A pin must be set in order to enable the output driver.
When OC0A is connected to the pin, the function of the COM0A1:0 bits depends on the
WGM02:0 bit setting. Table 73 shows the COM0A1:0 bit functionality when the
WGM02:0 bits are set to a normal or CTC mode (non-PWM).
Table 73. Compare Output Mode, non-PWM Mode
Table 74 shows the COM0A1:0 bit functionality when the WGM01:0 bits are set to fast
PWM mode.
Table 74. Compare Output Mode, Fast PWM Mode
Note:
Table 75 on page 131 shows the COM0A1:0 bit functionality when the WGM02:0 bits
are set to phase correct PWM mode.
Bit
0x24 (0x44)
Read/Write
Initial Value
COM0A1
COM0A1
0
0
1
1
0
0
1
1
1. A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case,
the Compare Match is ignored, but the set or clear is done at BOTTOM. See “Fast
PWM Mode” on page 125 for more details.
COM0A1
R/W
COM0A0
COM0A0
7
0
0
1
0
1
0
1
0
1
COM0A0
R/W
6
0
Description
Normal port operation, OC0A disconnected.
Toggle OC0A on Compare Match
Clear OC0A on Compare Match
Set OC0A on Compare Match
Description
Normal port operation, OC0A disconnected.
WGM02 = 0: Normal Port Operation, OC0A Disconnected.
WGM02 = 1: Toggle OC0A on Compare Match.
Clear OC0A on Compare Match, set OC0A at BOTTOM,
(non-inverting mode).
Set OC0A on Compare Match, clear OC0A at BOTTOM,
(inverting mode).
COM0B1
R/W
5
0
COM0B0
R/W
4
0
R
3
–
0
(1)
R
2
–
0
WGM01
R/W
1
0
WGM00
R/W
2549K–AVR–01/07
0
0
TCCR0A