an ADC conversion is initiated. See page 1091. Note that whether the GPIO is configured to trigger
on edge events or level events, a single-clock ADC trigger pulse is created in either event. Thus,
when a level event is selected, the ADC sample sequence will run only one time and multiple sample
sequences will not be executed if the level remains the same. It is recommended that edge events
be used as ADC trigger source.
Note that if the Port B
GPIOADCCTL
register is cleared, PB4 can still be used as an external trigger
for the ADC. This is a legacy mode which allows code written for previous devices to operate on
this microcontroller.
10.3.2.3
μDMA Trigger Source
Any GPIO pin can be configured to be an external trigger for the μDMA using the
GPIO DMA Control
(GPIODMACTL)
register. If any GPIO is configured as a non-masked interrupt pin (the appropriate
bit of
GPIOIM
is set), a
dma_req
signal is sent to the µDMA. If the μDMA is configured to start a
transfer based on the GPIO signal, a transfer is initiated. When transfer is complete, the
dma_done
signal is sent from the µDMA to the GPIO and is reported as a DMA (done) interrupt in the
GPIORIS
register.
10.3.2.4
HIB Wake Source
GPIO pins K[7:4] on Port K can be configured as an external wake source for the hibernation (HIB)
module. The pins can be configured in the following way:
1.
Write 0x0000.0040 to the
HIBCTL
register at offset 0x010 to enable 32.768-kHz Hibernation
oscillator.
2.
Write any data to be retained during power cut to the
HIBDATA
register at offsets 0x030-0x06F.
3.
Configure the
GPIOWAKEPEN
and
GPIOWAKELVL
registers at offsets 0x540 and 0x544 in
the GPIO module. Enable the I/O wake pad configuration by writing 0x0000.0001 to the
HIBIO
register at offset 0x010.
4.
When the
IOWRC
bit in the
HIBIO
register is read as 1, write 0x0000.0000 to the HIBO register
to lock the current pad configuration so that any other writes to the
GPIOWAKEPEN
and
GPIOWAKELVL
register will be ignored.
5.
The hibernation sequence may be initiated by writing 0x0000.0052 to the
HIBCTL
register.
The
GPIOWAKESTAT
register at offset 0x548 can be read to determine which port caused a wake
pin assertion.
10.3.3
Mode Control
The GPIO pins can be controlled by either software or hardware. Software control is the default for
most signals and corresponds to the GPIO mode, where the
GPIODATA
register is used to read
or write the corresponding pins. When hardware control is enabled via the
GPIO Alternate Function
Select (GPIOAFSEL)
register (see page 770), the pin state is controlled by its alternate function
(that is, the peripheral).
Further pin muxing options are provided through the
GPIO Port Control (GPIOPCTL)
register which
selects one of several peripheral functions for each GPIO. For information on the configuration
options, refer to Table 26-5 on page 1808.
Note:
If any pin is to be used as an ADC input, the appropriate bit in the
GPIOAMSEL
register
must be set to disable the analog isolation circuit.
751
June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller