Description of Operation
14-14
ADSP-BF537 Blackfin Processor Hardware Reference
The state of the GPIOs can be read through any of these data, set, clear, or
toggle registers. However, the returned value reflects the state of the input
pin only if the proper input enable bit in the
PORTxIO_INEN
register is set.
Note that GPIOs can still sense the state of the pin when the function
enable bits in the
PORTx_FER
registers are set.
Since function enable registers and GPIO input enable registers reset to
zero, no external pull-ups or pull-downs are required on the unused pins
of port F, port G, and port H.
GPIO Interrupt Processing
Each GPIO can be configured to generate an interrupt. The processor can
sense up to 48 asynchronous off-chip signals, requesting interrupts
through five interrupt channels. To make a pin function as an interrupt
pin, the associated input enable bit in the
PORTxIO_INEN
register must be
set. The function enable bit in the
PORTx_FER
register is typically cleared.
Then, an interrupt request can be generated according to the state of the
pin (either high or low), an edge transition (low to high or high to low), or
on both edge transitions (low to high and high to low). Input sensitivity is
defined on a per-bit basis by the GPIO polarity registers (
PORTFIO_POLAR
,
PORTGIO_POLAR,
and
PORTHIO_POLAR
), and the GPIO interrupt sensitivity
registers (
PORTFIO_EDGE
,
PORTGIO_EDGE
, and
PORTHIO_EDGE
). If configured
for edge sensitivity, the GPIO set on both edges registers (
PORTFIO_BOTH
,
PORTGIO_BOTH
, and
PORTHIO_BOTH
) let the interrupt request generate on
both edges.
The GPIO polarity registers are used to configure the polarity of the
GPIO input source. To select active high or rising edge, set the bits in the
GPIO polarity register to 0. To select active low or falling edge, set the
bits in the GPIO polarity register to 1. This register has no effect on
GPIOs that are defined as outputs. The contents of the GPIO polarity
registers are cleared at reset, defaulting to active high polarity.
Содержание Blackfin ADSP-BF537
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Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...