ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 131

• Manufacturer Part Number: ATMEGA644PV
• Description: 8-bit Microcontroller with 16/32/64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

14.11 Register Description
14.11.1
8011D–AVR–02/07
TCCR1A – Timer/Counter1 Control Register A
Figure 14-13. 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
The COMnA1:0 and COMnB1:0 control the Output Compare pins (OCnA and OCnB respec-
tively) behavior. If one or both of the COMnA1:0 bits are written 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 bit are written to one, the OCnB output overrides the normal port functionality of the
I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit correspond-
ing to the OCnA or OCnB pin must be set in order to enable the output driver.
When the OCnA or OCnB is connected to the pin, the function of the COMnx1:0 bits is depen-
dent of the WGMn3:0 bits setting.
when the WGMn3:0 bits are set to a Normal or a CTC mode (non-PWM).
Table 14-2.
Bit
(0x80)
Read/Write
Initial Value
COMnA1/COMnB1
and ICF n
(PC and PFC PWM)
TOVn
(CTC and FPWM)
(Update at TOP)
0
0
1
1
TCNTn
TCNTn
OCRnx
(clk
as TOP)
clk
clk
I/O
(FPWM)
I/O
Tn
/8)
(if used
COM1A1
Compare Output Mode, non-PWM
R/W
7
0
COM1A0
COMnA0/COMnB0
R/W
6
0
TOP - 1
TOP - 1
Old OCRnx Value
0
1
0
1
COM1B1
Table 14-2 on page 131
R/W
5
0
COM1B0
R/W
4
0
Description
Normal port operation, OCnA/OCnB disconnected.
Toggle OCnA/OCnB on Compare Match.
Clear OCnA/OCnB on Compare Match (Set output to
low level).
Set OCnA/OCnB on Compare Match (Set output to
high level).
TOP
TOP
ATmega164P/324P/644P
R
3
–
0
shows the COMnx1:0 bit functionality
BOTTOM
TOP - 1
clk_I/O
R
2
–
0
New OCRnx Value
/8)
WGM11
R/W
1
0
BOTTOM + 1
TOP - 2
WGM10
R/W
0
0
TCCR1A
131