Datasheet
169
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
15.12.3 TCCR4C – Timer/Counter4 Control Register C
• Bits 7,6 - COM4A1S, COM4A0S: Comparator A Output Mode, Bits 1 and 0
These bits are the shadow bits of the COM4A1 and COM4A0 bits that are described in the section “TCCR4A –
Timer/Counter4 Control Register A” on page 164.
• Bits 5,4 - COM4B1S, COM4B0S: Comparator B Output Mode, Bits 1 and 0
These bits are the shadow bits of the COM4A1 and COM4A0 bits that are described in the section “TCCR4A –
Timer/Counter4 Control Register A” on page 164.
• Bits 3,2 - COM4D1, COM4D0: Comparator D Output Mode, Bits 1 and 0
These bits control the behavior of the Waveform Output (OCW4D) and the connection of the Output Compare
pin (OC4D). If one or both of the COM4D1:0 bits are set, the OC4D output overrides the normal port
functionality of the I/O pin it is connected to. The complementary OC4D
output is connected only in PWM modes
when the COM4D1:0 bits are set to “01”. Note that the Data Direction Register (DDR) bit corresponding to the
OC4D pin must be set in order to enable the output driver.
The function of the COM4D1:0 bits depends on the PWM4D and WGM40 bit settings.
The table shows the COM4D1:0 bit functionality when the PWM4D bit is set to a Normal Mode (non-PWM).
The table shows the COM4D1:0 bit functionality when the PWM4D and WGM40 bits are set to Fast PWM Mode.
Bit 76543210
COM4A1S COM4A0S COM4B1S COMAB0S COM4D1 COM4D0 FOC4D PWM4D TCCR4C
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial value 00000000
Table 15-15. Compare Output Mode, Normal Mode (non-PWM)
COM4D1..0 OCW4D Behavior OC4D Pin OC4D 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 15-16. Compare Output Mode, Fast PWM Mode
COM4D1..0 OCW4D Behavior OC4D Pin OC4D Pin
00 Normal port operation Disconnected Disconnected
01
Cleared on Compare Match
Set when TCNT4 = 0x000
Connected Connected
10
Cleared on Compare Match
Set when TCNT4 = 0x000
Connected Disconnected
11
Set on Compare Match
Clear when TCNT4 = 0x000
Connected Disconnected