Rainbow Electronics ATtiny861_V - Manual (Page 113)

113
2588B–AVR–11/06
ATtiny261/461/861
16.11 Register Description
16.11.1 TCCR1A – Timer/Counter1 Control Register A
• Bits 7,6 - COM1A1, COM1A0: Comparator A Output Mode, Bits 1 and 0
These bits control the behaviour of the Waveform Output (OCW1A) and the connection of the
Output Compare pin (OC1A). If one or both of the COM1A1:0 bits are set, the OC1A 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 COM1A1:0 bits are set to “01”. Note
that the Data Direction Register (DDR) bit corresponding to the OC1A and OC1A pins must be
set in order to enable the output driver.
The function of the COM1A1:0 bits depends on the PWM1A, WGM10 and WGM11 bit settings.
Table 16-6 shows the COM1A1:0 bit functionality when the PWM1A bit is set to Normal Mode
(non-PWM).
Table 16-7 shows the COM1A1:0 bit functionality when the PWM1A, WGM10 and WGM11 bits
are set to fast PWM mode.
Bit 7 6 5 4 3 2 1 0
0x30 (0x50) COM1A1 COM1A0 COM1B1 COM1B0 FOC1A FOC1B PWM1A PWM1B TCCR1A
Read/Write R/W R/W R/W R/W W W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Table 16-6. Compare Output Mode, Normal Mode (non-PWM)
COM1A1..0 OCW1A Behaviour OC1A Pin OC1A 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 16-7. Compare Output Mode, Fast PWM Mode
COM1A1..0 OCW1A Behaviour OC1A OC1A
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