Datasheet
113
8197C–AVR–05/11
ATtiny261A/461A/861A
• Bits 5:4 – COM1B[1:0]: Comparator B Output Mode, Bits 1 and 0
These bits control the behaviour of the Waveform Output (OCW1B) and the connection of the
Output Compare pin (OC1B). If one or both of the COM1B[1:0] bits are set, the OC1B output
overrides the normal port functionality of the I/O pin it is connected to. The complementary
OC1B
output is connected only in PWM modes when the COM1B[1:0] bits are set to “01”. Note
that the Data Direction Register (DDR) bit corresponding to the OC1B pin must be set in order to
enable the output driver.
The function of the COM1B[1:0] bits depends on the PWM1B and WGM1[1:0] bit settings. Table
12-13 shows the COM1B[1:0] bit functionality when the PWM1B bit is set to Normal Mode (non-
PWM).
Table 12-14 shows the COM1B[1:0] bit functionality when the PWM1B and WGM1[1:0] bits are
set to Fast PWM Mode.
Table 12-15 shows the COM1B[1:0] bit functionality when the PWM1B and WGM1[1:0] bits are
set to Phase and Frequency Correct PWM Mode.
Bits COM1B1 and COM1B0 are shadowed in TCCR1C. Writing to bits COM1B1 and COM1B0
will also change bits COM1B1S and COM1B0S in TCCR1C. Similary, changes written to bits
Table 12-13. Compare Output Mode, Normal Mode (non-PWM)
COM1B[1:0] OCW1B Behaviour OC1B Pin OC1B Pin
00 Normal port operation. Disconnected Disconnected
01 Toggle on Compare Match. Connected Disconnected
10 Clear on Compare Match. Connected Disconnected
11 Set on Compare Match. Connected Disconnected
Table 12-14. Compare Output Mode, Fast PWM Mode
COM1B[1:0] OCW1B Behaviour OC1B Pin OC1B Pin
00 Normal port operation. Disconnected Disconnected
01
Cleared on Compare Match.
Set when TCNT1 = 0x000.
Connected Connected
10
Cleared on Compare Match.
Set when TCNT1 = 0x000.
Connected Disconnected
11
Set on Compare Match.
Cleared when TCNT1 = 0x000.
Connected Disconnected
Table 12-15. Compare Output Mode, Phase and Frequency Correct PWM Mode
COM1B[1:0] OCW1B Behaviour OC1B Pin OC1B Pin
00 Normal port operation. Disconnected Disconnected
01
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected Connected
10
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected Disconnected
11
Set on Compare Match when up-counting.
Cleared on Compare Match when down-counting.
Connected Disconnected