ADSP-BF537 Blackfin Processor Hardware Reference
14-11
General-Purpose Ports
The GPIO direction registers are read-write registers with each bit posi-
tion corresponding to a particular GPIO. A logic 1 configures a GPIO as
an output, driving the state contained in the GPIO data register if the
peripheral function is not enabled by the function enable registers. A logic
0 configures a GPIO as an input.
L
Note when using the GPIO as an input, the corresponding bit
should also be set in the GPIO input enable register. Otherwise,
changes at the input pins will not be recognized by the processor.
The GPIO input enable registers (
PORTFIO_INEN
,
PORTGIO_INEN
, and
PORTHIO_INEN
) are used to enable the input buffers on any GPIO that is
being used as an input. Leaving the input buffer disabled eliminates the
need for pull-ups and pull-downs when a particular
PFx
,
PGx
, or
PHx
pin is
not used in the system. By default, the input buffers are disabled.
a
Once the input driver of a GPIO pin is enabled, the GPIO is not
allowed to operate as an output anymore. Never enable the input
driver (by setting
PORTxIO_INEN
bits) and the output driver (by set-
ting
PORTxIO_DIR
bits) for the same GPIO.
A write operation to any of the GPIO data registers sets the value of all
GPIOs in this port that are configured as outputs. GPIOs configured as
inputs ignore the written value. A read operation returns the state of the
GPIOs defined as outputs and the sense of the inputs, based on the polar-
ity and sensitivity settings, if their input buffers are enabled.
helps to interpret read values in GPIO mode, based on the settings of the
PORTxIO_POLAR
,
PORTxIO_EDGE
, and
PORTxIO_BOTH
registers.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...