LM3S6950 Datasheet, PDF (159/524 Pages) List of Unclassifed Manufacturers – Microcontroller

LM3S6950 Microcontroller
9.1.3
9.1.4
9.1.5
9.1.6
9.2
■ GPIO Interrupt Sense (GPIOIS) register (see page 165)
■ GPIO Interrupt Both Edges (GPIOIBE) register (see page 166)
■ GPIO Interrupt Event (GPIOIEV) register (see page 167)
Interrupts are enabled/disabled via the GPIO Interrupt Mask (GPIOIM) register (see page 168).
When an interrupt condition occurs, the state of the interrupt signal can be viewed in two locations:
the GPIO Raw Interrupt Status (GPIORIS) and GPIO Masked Interrupt Status (GPIOMIS) registers
(see page 169 and page 170). As the name implies, the GPIOMIS register only shows interrupt
conditions that are allowed to be passed to the controller. The GPIORIS register indicates that a
GPIO pin meets the conditions for an interrupt, but has not necessarily been sent to the controller.
Interrupts are cleared by writing a 1 to the GPIO Interrupt Clear (GPIOICR) register (see page 171).
When programming the following interrupt control registers, the interrupts should be masked (GPIOIM
set to 0). Writing any value to an interrupt control register (GPIOIS, GPIOIBE, or GPIOIEV) can
generate a spurious interrupt if the corresponding bits are enabled.
Mode Control
The GPIO pins can be controlled by either hardware or software. When hardware control is enabled
via the GPIO Alternate Function Select (GPIOAFSEL) register (see page 172), the pin state is
controlled by its alternate function (that is, the peripheral). Software control corresponds to GPIO
mode, where the GPIODATA register is used to read/write the corresponding pins.
Commit Control
The commit control registers provide a layer of protection against accidental programming of critical
hardware peripherals. Writes to protected bits of the GPIO Alternate Function Select (GPIOAFSEL)
register (see page 172) are not committed to storage unless the GPIO Lock (GPIOLOCK) register
(see page 182) has been unlocked and the appropriate bits of the GPIO Commit (GPIOCR) register
(see page 183) have been set to 1.
Pad Control
The pad control registers allow for GPIO pad configuration by software based on the application
requirements. The pad control registers include the GPIODR2R, GPIODR4R, GPIODR8R, GPIOODR,
GPIOPUR, GPIOPDR, GPIOSLR, and GPIODEN registers.
Identification
The identification registers configured at reset allow software to detect and identify the module as
a GPIO block. The identification registers include the GPIOPeriphID0-GPIOPeriphID7 registers as
well as the GPIOPCellID0-GPIOPCellID3 registers.
Initialization and Configuration
To use the GPIO, the peripheral clock must be enabled by setting the appropriate GPIO Port bit
field (GPIOn) in the RCGC2 register.
On reset, all GPIO pins (except for the five JTAG pins) are configured out of reset to be undriven
(tristate): GPIOAFSEL=0, GPIODEN=0, GPIOPDR=0, and GPIOPUR=0. Table 9-1 on page 160
shows all possible configurations of the GPIO pads and the control register settings required to
achieve them. Table 9-2 on page 160 shows how a rising edge interrupt would be configured for pin
2 of a GPIO port.
June 14, 2007
159
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