ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 156

• Manufacturer Part Number: ATMEga64L
• Description: 8-bit AVR Microcontroller with 64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

156
ATmega64(L)
Table 64. Waveform Generation Mode Bit Description
Note:
• Bit 5:4 – COM21:0: Compare Match Output Mode
These bits control the Output Compare pin (OC2) behavior. If one or both of the
COM21:0 bits are set, the OC2 output overrides the normal port functionality of the I/O
pin it is connected to. However, note that the Data Direction Register (DDR) bit corre-
sponding to the OC2 pin must be set in order to enable the output driver.
When OC2 is connected to the pin, the function of the COM21:0 bits depends on the
WGM21:0 bit setting. Table 65 shows the COM21:0 bit functionality when the WGM21:0
bits are set to a Normal or CTC mode (non-PWM).
Table 65. Compare Output Mode, non-PWM Mode
Table 66 shows the COM21:0 bit functionality when the WGM21:0 bits are set to fast
PWM mode.
Table 66. Compare Output Mode, Fast PWM Mode
Note:
Table 67 shows the COM21:0 bit functionality when the WGM21:0 bits are set to phase
correct PWM mode.
Mode
0
1
2
3
COM21
COM21
0
0
1
1
0
0
1
1
1. The CTC2 and PWM2 bit definition names are now obsolete. Use the WGM21:0 def-
1. A special case occurs when OCR2 equals TOP and COM21 is set. In this case, the
WGM21
(CTC2)
initions. However, the functionality and location of these bits are compatible with
previous versions of the timer.
Compare Match is ignored, but the set or clear is done at TOP. See “Fast PWM
Mode” on page 150 for more details.
0
0
1
1
COM20
COM20
WGM20
(PWM2)
0
1
0
1
0
1
0
1
0
1
0
1
Description
Normal port operation, OC2 disconnected.
Toggle OC2 on Compare Match.
Clear OC2 on Compare Match.
Set OC2 on Compare Match.
Description
Normal port operation, OC2 disconnected.
Reserved
Clear OC2 on Compare Match, set OC2 at TOP.
Set OC2 on Compare Match, clear OC2 at TOP.
Timer/Counter Mode
of Operation
Normal
PWM, Phase Correct
CTC
Fast PWM
(1)
TOP
0xFF
0xFF
OCR2
0xFF
(1)
Update of
OCR2
Immediate
TOP
Immediate
TOP
2490G–AVR–03/04
TOV2 Flag
Set on
MAX
BOTTOM
MAX
MAX