
70
1477K–AVR–08/10
ATtiny26(L)
Timer/Counter1
Control Register A –
TCCR1A
Bits 7, 6 – COM1A1, COM1A0: Comparator A Output Mode, Bits 1 and 0
The COM1A1 and COM1A0 control bits determine any output pin action following a Compare
Match with Compare Register A in Timer/Counter1. Output pin actions affect pin PB1 (OC1A).
Since this is an alternative function to an I/O port, the corresponding direction control bit must be
set (one) in order to control an output pin. Note that OC1A is not connected in normal mode.
description.
Bits 5, 4 – COM1B1, COM1B0: Comparator B Output Mode, Bits 1 and 0
The COM1B1 and COM1B0 control bits determine any output pin action following a Compare
Match with Compare Register B in Timer/Counter1. Output pin actions affect pin PB3 (OC1B).
Since this is an alternative function to an I/O port, the corresponding direction control bit must be
set (one) in order to control an output pin. Note that OC1B is not connected in normal mode.
description.
Bit 3 – FOC1A: Force Output Compare Match 1A
Writing a logical one to this bit forces a change in the Compare Match output pin PB1 (OC1A)
according to the values already set in COM1A1 and COM1A0. If COM1A1 and COM1A0 written
in the same cycle as FOC1A, the new settings will be used. The Force Output Compare bit can
be used to change the output pin value regardless of the timer value. The automatic action pro-
grammed in COM1A1 and COM1A0 takes place as if a compare match had occurred, but no
interrupt is generated. The FOC1A bit always reads as zero. FOC1A is not in use if PWM1A bit
is set.
Bit 2 – FOC1B: Force Output Compare Match 1B
Writing a logical one to this bit forces a change in the Compare Match output pin PB3 (OC1B)
according to the values already set in COM1B1 and COM1B0. If COM1B1 and COM1B0 written
in the same cycle as FOC1B, the new settings will be used. The Force Output Compare bit can
Bit
7
6
5
4
3
2
1
0
$30 ($50)
COM1A1
COM1A0
COM1B1
COM1B0
FOC1A
FOC1B
PWM1A
PWM1B
TCCR1A
Read/Write
R/W
Initial Value
0
Table 32. Comparator A Mode Select
COM1A1
COM1A0
Description
0
Timer/Counter Comparator A disconnected from output pin OC1A.
0
1
Toggle the OC1A output line.
1
0
Clear the OC1A output line.
1
Set the OC1A output line.
Table 33. Comparator B Mode Select
COM1B1
COM1B0
Description
0
Timer/Counter Comparator B disconnected from output pin OC1B.
0
1
Toggle the OC1B output line.
1
0
Clear the OC1B output line.
1
Set the OC1B output line.