46
ATmega103(L)
0945G–09/01
If the Noise Canceler function is enabled, the actual trigger condition for the capture
event is monitored over four samples, and all four must be equal to activate the capture
flag.
Timer/Counter1 Control
Register A – TCCR1A
• Bits 7..6 – COM1A1, COM1A0: Compare Output Mode1A, Bits 1 and 0
The COM1A1 and COM1A0 control bits determine any output pin action following a
compare match in Timer/Counter1. Any output pin actions affect pin OC1A – Output
CompareA pin 1. This is an alternative function to an I/O port, and the corresponding
direction control bit must be set (one) to control an output pin. The control configuration
is shown in Table 15
• Bits 5..4 – COM1B1, COM1B0: Compare Output Mode1B, Bits 1 and 0
The COM1B1 and COM1B0 control bits determine any output pin action following a
compare match in Timer/Counter1. Any output pin actions affect pin OC1B – Output
CompareB. Since this is an alternative function to an I/O port, the corresponding direc-
tion control bit must be set (one) to control an output pin. The control configuration is
given in Table 15.
Note:
X = A or B.
In PWM mode, these bits have a different function. Refer to Table 16 for a detailed
description.
• Bits 3..2 – Res: Reserved Bits
These bits are reserved bits in the ATmega103(L) and always read as zero.
• Bits 1..0 – PWM11, PWM10: Pulse Width Modulator Select Bits
These bits select PWM operation of Timer/Counter1 as specified in Table 18 on page
50. This mode is described on page 50.
Bit
7
6
5
4
3
2
1
0
$2F ($4F)
COM1A1
COM1A0
COM1B1
COM1B0
–
–
PWM11
PWM10
TCCR1A
Read/Write
R/W
R/W
R/W
R/W
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Table 15.
Compare1 Mode Select
COM1X1
COM1X0
Description
0
0
Timer/Counter1 disconnected from output pin OC1X
0
1
Toggle the OC1X output line.
1
0
Clear the OC1X output line (to zero).
1
1
Set the OC1X output line (to one).
Table 16.
PWM Mode Select
PWM11
PWM10
Description
0
0
PWM operation of Timer/Counter1 is disabled.
0
1
Timer/Counter1 is an 8-bit PWM.
1
0
Timer/Counter1 is a 9-bit PWM.
1
1
Timer/Counter1 is a 10-bit PWM.