ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 131

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

16-bit Timer/Counter
Register Description
Timer/Counter1 Control
Register A – TCCR1A
Timer/Counter3 Control
Register A – TCCR3A
2490G–AVR–03/04
Figure 58. Timer/Counter Timing Diagram, with Prescaler (f
• 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
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 writ-
ten 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 functionality 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 func-
tionality of the I/O pin it is connected to. However, 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. Table 58 shows the COMnx1:0 bit func-
tionality when the WGMn3:0 bits are set to a Normal or a CTC mode (non-PWM).
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
(PC and PFC PWM)
and ICFn
(CTC and FPWM)
(Update at TOP)
TOVn
TCNTn
TCNTn
OCRnx
(clk
as TOP)
clk
clk
I/O
(FPWM)
I/O
Tn
/8)
(if used
COM1A1
COM3A1
R/W
R/W
7
0
7
0
COM1A0
COM3A0
R/W
R/W
6
0
6
0
TOP - 1
TOP - 1
Old OCRnx Value
COM1B1
COM3B1
R/W
R/W
5
0
5
0
COM1B0
COM3B0
R/W
R/W
4
0
4
0
TOP
TOP
COM1C1
COM3C1
R/W
R/W
3
0
3
0
COM1C0
COM3C0
R/W
R/W
2
0
2
0
BOTTOM
TOP - 1
clk_I/O
ATmega64(L)
New OCRnx Value
WGM11
WGM31
R/W
R/W
/8)
1
0
1
0
WGM10
WGM30
R/W
R/W
0
0
0
0
BOTTOM + 1
TOP - 2
TCCR1A
TCCR3A
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