LM3S2276 Datasheet, PDF (348/785 Pages) Texas Instruments – Stellaris® LM3S2276 Microcontroller

General-Purpose Input/Outputs (GPIOs)
9 General-Purpose Input/Outputs (GPIOs)
The GPIO module is composed of five physical GPIO blocks, each corresponding to an individual
GPIO port (Port A, Port B, Port C, Port D, Port E). The GPIO module supports 0-33 programmable
input/output pins, depending on the peripherals being used.
The GPIO module has the following features:
■ 0-33 GPIOs, depending on configuration
■ 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 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 be configured
with an 18-mA pad drive for high-current applications
– Slew rate control for the 8-mA drive
– Open drain enables
– Digital input enables
9.1 Signal Description
GPIO signals have alternate hardware functions. Table 9-3 on page 350 lists the GPIO pins and their
analog and digital alternate functions. The AINx 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. The digital alternate hardware
functions are enabled by setting the appropriate bit in the GPIO Alternate Function Select
(GPIOAFSEL) and GPIODEN registers and configuring the PMCx bit field in the GPIO Port Control
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November 17, 2011
Texas Instruments-Production Data