ATMEGA48V_11 ATMEL [ATMEL Corporation], ATMEGA48V_11 Datasheet - Page 94

• Manufacturer Part Number: ATMEGA48V_11
• Description: 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

15.6.1
15.7
2545T–AVR–05/11
Modes of operation
Compare output mode and waveform generation
Figure 15-4. Compare match output unit, schematic.
The general I/O port function is overridden by the Output Compare (OC0x) from the Waveform
Generator if either of the COM0x1:0 bits are set. However, the OC0x pin direction (input or out-
put) is still controlled by the Data Direction Register (DDR) for the port pin. The Data Direction
Register bit for the OC0x pin (DDR_OC0x) must be set as output before the OC0x value is visi-
ble on the pin. The port override function is independent of the Waveform Generation mode.
The design of the Output Compare pin logic allows initialization of the OC0x state before the out-
put is enabled. Note that some COM0x1:0 bit settings are reserved for certain modes of
operation.
The Waveform Generator uses the COM0x1:0 bits differently in Normal, CTC, and PWM modes.
For all modes, setting the COM0x1:0 = 0 tells the Waveform Generator that no action on the
OC0x Register is to be performed on the next compare match. For compare output actions in the
non-PWM modes refer to
page
A change of the COM0x1:0 bits state will have effect at the first compare match after the bits are
written. For non-PWM modes, the action can be forced to have immediate effect by using the
FOC0x strobe bits.
The mode of operation, that is, the behavior of the Timer/Counter and the Output Compare pins,
is defined by the combination of the Waveform Generation mode (WGM02:0) and Compare Out-
put mode (COM0x1:0) bits. The Compare Output mode bits do not affect the counting sequence,
while the Waveform Generation mode bits do. The COM0x1:0 bits control whether the PWM out-
put generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes
the COM0x1:0 bits control whether the output should be set, cleared, or toggled at a compare
match
For detailed timing information refer to
101, and for phase correct PWM refer to
(See “Compare match output unit” on page
See “Register description” on page 101.
COMnx1
COMnx0
FOCn
clk
I/O
Table 15-2 on page
Waveform
generator
“Timer/counter timing diagrams” on page
D
D
D
Table 15-4 on page
PORT
101. For fast PWM mode, refer to
DDR
OCnx
93.).
Q
Q
Q
ATmega48/88/168
1
0
102.
99.
OCnx
pin
Table 15-3 on
94