Datasheet

31
XMEGA A4U [DATASHEET]
Atmel-8387H-AVR-ATxmega16A4U-34A4U-64A4U-128A4U-Datasheet_09/2014
15. I/O Ports
15.1 Features
z 34 general purpose input and output pins with individual configuration
z Output driver with configurable driver and pull settings:
z Totem-pole
z Wired-AND
z Wired-OR
z Bus-keeper
z Inverted I/O
z Input with synchronous and/or asynchronous sensing with interrupts and events
z Sense both edges
z Sense rising edges
z Sense falling edges
z Sense low level
z Optional pull-up and pull-down resistor on input and Wired-OR/AND configurations
z Optional slew rate control
z Asynchronous pin change sensing that can wake the device from all sleep modes
z Two port interrupts with pin masking per I/O port
z Efficient and safe access to port pins
z Hardware read-modify-write through dedicated toggle/clear/set registers
z Configuration of multiple pins in a single operation
z Mapping of port registers into bit-accessible I/O memory space
z Peripheral clocks output on port pin
z Real-time counter clock output to port pin
z Event channels can be output on port pin
z Remapping of digital peripheral pin functions
z Selectable USART, SPI, and timer/counter input/output pin locations
15.2 Overview
One port consists of up to eight port pins: pin 0 to 7. Each port pin can be configured as input or output with
configurable driver and pull settings. They also implement synchronous and asynchronous input sensing with
interrupts and events for selectable pin change conditions. Asynchronous pin-change sensing means that a pin
change can wake the device from all sleep modes, included the modes where no clocks are running.
All functions are individual and configurable per pin, but several pins can be configured in a single operation. The pins
have hardware read-modify-write (RMW) functionality for safe and correct change of drive value and/or pull resistor
configuration. The direction of one port pin can be changed without unintentionally changing the direction of any other
pin.
The port pin configuration also controls input and output selection of other device functions. It is possible to have both
the peripheral clock and the real-time clock output to a port pin, and available for external use. The same applies to
events from the event system that can be used to synchronize and control external functions. Other digital
peripherals, such as USART, SPI, and timer/counters, can be remapped to selectable pin locations in order to
optimize pin-out versus application needs.
The notation of the ports are PORTA, PORTB, PORTC, PORTD, PORTE, and PORTR.
15.3 Output Driver
All port pins (Pn) have programmable output configuration. The port pins also have configurable slew rate limitation to
reduce electromagnetic emission.