ATMEGA64-16MC Atmel, ATMEGA64-16MC Datasheet - Page 151

• Manufacturer Part Number: ATMEGA64-16MC
• Description: IC AVR MCU 64K 16MHZ COM 64-QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA64-16MC

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 64-MLF®, 64-QFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Compare Output Mode
and Waveform
Generation
Modes of
Operation
Normal Mode
Clear Timer on
Compare Match (CTC)
Mode
2490Q–AVR–06/10
ter bit for the OC2 pin (DDR_OC2) must be set as output before the OC2 value is visible 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 OC2 state before the out-
put is enabled. Note that some COM21:0 bit settings are reserved for certain modes of
operation.
The Waveform Generator uses the COM21:0 bits differently in Normal, CTC, and PWM modes.
For all modes, setting the COM21:0 = 0 tells the Waveform Generator that no action on the OC2
Register is to be performed on the next Compare Match. For compare output actions in the non-
PWM modes refer to
and for phase correct PWM refer to
A change of the COM21:0 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
FOC2 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 (WGM21:0) and Compare Out-
put mode (COM21:0) bits. The Compare Output mode bits do not affect the counting sequence,
while the Waveform Generation mode bits do. The COM21:0 bits control whether the PWM out-
put generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes
the COM21:0 bits control whether the output should be set, cleared, or toggled at a Compare
Match (see “Compare Match Output Unit” on page 150).
For detailed timing information refer to
“Timer/Counter Timing Diagrams” on page
The simplest mode of operation is the Normal mode (WGM21:0 = 0). In this mode the counting
direction is always up (incrementing), and no counter clear is performed. The counter simply
overruns when it passes its maximum 8-bit value (TOP = 0xFF) and then restarts from the bot-
tom (0x00). In normal operation the Timer/Counter Overflow Flag (TOV2) will be set in the same
timer clock cycle as the TCNT2 becomes zero. The TOV2 flag in this case behaves like a ninth
bit, except that it is only set, not cleared. However, combined with the timer overflow interrupt
that automatically clears the TOV2 flag, the timer resolution can be increased by software. There
are no special cases to consider in the Normal mode, a new counter value can be written
anytime.
The Output Compare unit can be used to generate interrupts at some given time. Using the Out-
put Compare to generate waveforms in Normal mode is not recommended, since this will
occupy too much of the CPU time.
In Clear Timer on Compare or CTC mode (WGM21:0 = 2), the OCR2 Register is used to manip-
ulate the counter resolution. In CTC mode the counter is cleared to zero when the counter value
(TCNT2) matches the OCR2. The OCR2 defines the top value for the counter, hence also its
resolution. This mode allows greater control of the Compare Match output frequency. It also sim-
plifies the operation of counting external events.
The timing diagram for the CTC mode is shown in
increases until a Compare Match occurs between TCNT2 and OCR2, and then counter (TCNT2)
is cleared.
See “8-bit Timer/Counter Register Description” on page 157.
Table 65 on page
Table 67 on page
158. For fast PWM mode, refer to
Figure
155.
68,
Figure
159.
Figure
69,
65. The counter value (TCNT2)
Figure
ATmega64(L)
Table 66 on page
70, and
Figure 71
158,
151
in