Datasheet

167
7766F–AVR–11/10
ATmega16/32U4
• 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 sec-
tion “TCCR4A – Timer/Counter4 Control Register A” on page 162.
• 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. Table 15-
16 shows the COM4D1:0 bit functionality when the PWM4D bit is set to a Normal Mode (non-
PWM).
Table 15-17 shows the COM4D1:0 bit functionality when the PWM4D and WGM40 bits are set
to Fast PWM Mode.
Table 15-18 on page 168 shows the COM4D1:0 bit functionality when the PWM4D and WGM40
bits are set to Phase and Frequency Correct PWM Mode.
Table 15-16. 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 15-17. 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