LM3S9781_15 Datasheet, PDF (392/1271 Pages) Texas Instruments – Stellaris LM3S9781 Microcontroller

General-Purpose Input/Outputs (GPIOs)
8 General-Purpose Input/Outputs (GPIOs)
The GPIO module is composed of nine physical GPIO blocks, each corresponding to an individual
GPIO port (Port A, Port B, Port C, Port D, Port E, Port F, Port G, Port H, Port J). The GPIO module
supports up to 65 programmable input/output pins, depending on the peripherals being used.
The GPIO module has the following features:
■ Up to 65 GPIOs, depending on configuration
■ Highly flexible pin muxing allows use as GPIO or one of several peripheral functions
■ 5-V-tolerant in input configuration
■ Two means of port access: either Advanced High-Performance Bus (AHB) with better back-to-back
access performance, or the legacy Advanced Peripheral Bus (APB) for backwards-compatibility
with existing code
■ Fast toggle capable of a change every clock cycle for ports on AHB, every two clock cycles for
ports on APB
■ Programmable control for GPIO interrupts
– Interrupt generation masking
– Edge-triggered on rising, falling, or both
– Level-sensitive on High or Low values
■ Bit masking in both read and write operations through address lines
■ Can be used to initiate an ADC sample sequence
■ Pins configured as digital inputs are Schmitt-triggered
■ Programmable control for GPIO pad configuration
– Weak pull-up or pull-down resistors
– 2-mA, 4-mA, and 8-mA pad drive for digital communication; up to four pads can sink 18-mA
for high-current applications
– Slew rate control for the 8-mA drive
– Open drain enables
– Digital input enables
8.1 Signal Description
GPIO signals have alternate hardware functions. The following table lists the GPIO pins and their
analog and digital alternate functions. The AINx and VREFA analog signals are not 5-V tolerant and
go through an isolation circuit before reaching their circuitry. These signals are configured by clearing
the corresponding DEN bit in the GPIO Digital Enable (GPIODEN) register and setting the
corresponding AMSEL bit in the GPIO Analog Mode Select (GPIOAMSEL) register. Other analog
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