XMEGA A4U [DATASHEET]
Atmel-8387G-AVR-ATxmega16A4U-34A4U-64A4U-128A4U-Datasheet_03/2014
30
15.
I/O Ports
15.1
Features
34 general purpose input and output pins with individual configuration
Output driver with configurable driver and pull settings:
Totem-pole
Wired-AND
Wired-OR
Bus-keeper
Inverted I/O
Input with synchronous and/or asynchronous sensing with interrupts and events
Sense both edges
Sense rising edges
Sense falling edges
Sense low level
Optional pull-up and pull-down resistor on input and Wired-OR/AND configurations
Optional slew rate control
Asynchronous pin change sensing that can wake the device from all sleep modes
Two port interrupts with pin masking per I/O port
Efficient and safe access to port pins
Hardware read-modify-write through dedicated toggle/clear/set registers
Configuration of multiple pins in a single operation
Mapping of port registers into bit-accessible I/O memory space
Peripheral clocks output on port pin
Real-time counter clock output to port pin
Event channels can be output on port pin
Remapping of digital peripheral pin functions
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.