LM3S8971 Luminary Micro, Inc, LM3S8971 Datasheet - Page 172

• Manufacturer Part Number: LM3S8971
• Description: Lm3s8971 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

General-Purpose Input/Outputs (GPIOs)
9.2
Table 9-1. GPIO Pad Configuration Examples
a. X=Ignored (don’t care bit)
?=Can be either 0 or 1, depending on the configuration
Table 9-2. GPIO Interrupt Configuration Example
172
Configuration
Digital Input (GPIO)
Digital Output (GPIO)
Open Drain Input
(GPIO)
Open Drain Output
(GPIO)
Digital Input (Timer
CCP)
Digital Input (QEI)
Digital Output (PWM)
Digital Output (Timer
PWM)
Digital Input/Output
(SSI)
Digital Input/Output
(UART)
Analog Input
(Comparator)
Digital Output
(Comparator)
Register
GPIOIS
GPIOIBE
Desired
Interrupt
Event
Trigger
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 172
shows all possible configurations of the GPIO pads and the control register settings required to
achieve them. Table 9-2 on page 172 shows how a rising edge interrupt would be configured for pin
2 of a GPIO port.
0=single
0=edge
1=level
1=both
edges
edge
GPIO Register Bit Value
AFSEL
0
0
0
0
1
1
1
1
1
1
0
1
Pin 2 Bit Value
7
X
X
DIR
X
X
X
X
X
X
X
0
1
0
1
0
6
a
ODR
X
X
a
0
0
1
1
0
0
0
0
0
0
0
0
5
DEN
X
X
Preliminary
1
1
1
1
1
1
1
1
1
1
0
1
PUR
4
?
?
X
X
?
?
?
?
?
?
0
?
X
X
PDR
3
?
?
X
X
?
?
?
?
?
?
0
?
X
X
DR2R
X
X
X
X
X
?
?
?
?
?
?
?
2
0
0
DR4R
X
X
X
X
X
?
?
?
?
?
?
?
1
DR8R
X
X
X
X
X
X
X
?
?
?
?
?
?
?
July 26, 2008
0
SLR
X
X
X
X
X
X
X
?
?
?
?
?
?
?