LM3S9997 Datasheet, PDF (328/1218 Pages) Texas Instruments – Stellaris® LM3S9997 Microcontroller

General-Purpose Input/Outputs (GPIOs)
10
10.1
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 60 programmable input/output pins, depending on the peripherals being used.
The GPIO module has the following features:
■ Up to 60 GPIOs, depending on configuration
■ Highly flexible pin muxing allows use as GPIO or one of several peripheral functions
■ 5-V-tolerant input/outputs
■ Fast toggle capable of a change every two clock cycles
■ 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
■ 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 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
Signal Description
GPIO signals have alternate hardware functions. Table 10-2 on page 329 and Table 10-3 on page 331
list 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 signals are 5-V tolerant and are connected directly to their circuitry (C0-,
328
June 15, 2010
Texas Instruments-Advance Information