9 register description, 1 tccr0a – timer/counter control register a, 2 tccr1a – timer/counter control register a – Rainbow Electronics ATtiny43U User Manual
Page 90: Attiny43u, Table 12-2. compare output mode, non-pwm mode
90
8048B–AVR–03/09
ATtiny43U
Figure 12-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Pres-
caler (f
clk_I/O
/8)
12.9
Register Description
12.9.1
TCCR0A – Timer/Counter Control Register A
12.9.2
TCCR1A – Timer/Counter Control Register A
• Bits 7:6 – COMnA[1:0]: Compare Match Output A Mode
These bits control the Output Compare pin (OCnA) behavior. If one or both of the COMnA[1:0]
bits are set, the OCnA output overrides the normal port functionality of the I/O pin it is connected
to. However, note that the Data Direction Register (DDR) bit corresponding to the OCnA pin
must be set in order to enable the output driver.
When OCnA is connected to the pin, the function of the COMnA[1:0] bits depends on the
WGMn[2:0] bit setting.
shows the COMnA[1:0] bit functionality when the
WGMn[2:0] bits are set to a normal or CTC mode (non-PWM).
OCFnx
OCRnx
TCNTn
(CTC)
TOP
TOP - 1
TOP
BOTTOM
BOTTOM + 1
clk
I/O
clk
Tn
(clk
I/O
/8)
Bit
7
6
5
4
3
2
1
0
COM0A1
COM0A0
COM0B1
COM0B0
–
–
WGM01
WGM00
TCCR0A
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
Bit
7
6
5
4
3
2
1
0
COM1A1
COM1A0
COM1B1
COM1B0
–
–
WGM11
WGM10
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 12-2.
Compare Output Mode, non-PWM Mode
COMnA1
COMnA0
Description
0
0
Normal port operation, OCnA disconnected.
0
1
Toggle OCnA on Compare Match
1
0
Clear OCnA on Compare Match
1
1
Set OCnA on Compare Match