Datasheet

ATmega16U4/32U4 [DATASHEET]

Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016

• T1/OC.4D/ADC9 – Port D, Bit 6

T1, Timer/Counter1 counter source.

OC.4D

: Timer 4 Output Compare D. This pin can be used to generate a high-speed PWM signal from Timer 4

module, complementary to OC.4D (PD7) signal. The pin has to be configured as an output (DDD6 set “one”) to

serve this function.

ADC9: Analog to Digital Converter, Channel 9

• XCK1/CTS – Port D, Bit 5

XCK1, USART1 External clock. The Data Direction Register (DDD5) controls whether the clock is output (DDD5

set) or input (DDD5 cleared). The XCK1 pin is active only when the USART1 operates in Synchronous mode.

CTS

: Clear-To-Send flow control signal used by enhanced UART module.

• ICP1/ADC8 – Port D, Bit 4

ICP1 – Input Capture Pin 1: The PD4 pin can act as an input capture pin for Timer/Counter1.

ADC8: Analog to Digital Converter, Channel 8

•INT3/TXD1 – Port D, Bit 3

INT3, External Interrupt source 3: The PD3 pin can serve as an external interrupt source to the MCU.

TXD1, Transmit Data (Data output pin for the USART1). When the USART1 Transmitter is enabled, this pin is

configured as an output regardless of the value of DDD3.

•INT2/RXD1 – Port D, Bit 2

INT2, External Interrupt source 2. The PD2 pin can serve as an External Interrupt source to the MCU.

RXD1, Receive Data (Data input pin for the USART1). When the USART1 receiver is enabled this pin is

configured as an input regardless of the value of DDD2. When the USART forces this pin to be an input, the

pull-up can still be controlled by the PORTD2 bit.

•INT1/SDA – Port D, Bit 1

INT1, External Interrupt source 1. The PD1 pin can serve as an external interrupt source to the MCU.

SDA, 2-wire Serial Interface Data: When the TWEN bit in TWCR is set (one) to enable the 2-wire Serial

Interface, pin PD1 is disconnected from the port and becomes the Serial Data I/O pin for the 2-wire Serial

Interface. In this mode, there is a spike filter on the pin to suppress spikes shorter than 50ns on the input signal,

and the pin is driven by an open drain driver with slew-rate limitation.

•INT0/SCL/OC0B – Port D, Bit 0

INT0, External Interrupt source 0. The PD0 pin can serve as an external interrupt source to the MCU.

SCL, 2-wire Serial Interface Clock: When the TWEN bit in TWCR is set (one) to enable the 2-wire Serial

Interface, pin PD0 is disconnected from the port and becomes the Serial Clock I/O pin for the 2-wire Serial

Interface. In this mode, there is a spike filter on the pin to suppress spikes shorter than 50ns on the input signal,

and the pin is driven by an open drain driver with slew-rate limitation.

OC.0B: Timer 0 Output Compare B. This pin can be used to generate a PWM signal from the Timer 0 module.

The two following tables relate the alternate functions of Port D to the overriding signals shown in Figure 10-5 on

page 72.