ADSP-BF50x Blackfin Processor Hardware Reference
9-15
General-Purpose Ports
For GPIOs configured as edge-sensitive, a readback of 1 from one
of these registers is sticky. That is, once it is set it remains set until
cleared by user code. For level-sensitive GPIOs, the pin state is
checked every cycle, so the readback value will change when the
original level on the pin changes.
The state of the output is reflected on the associated pin only if the func-
tion enable bit in the
PORTx_FER
register is cleared.
Write operations to the GPIO data registers modify the state of all GPIOs
of a port. In cases where only one or a few GPIOs need to be changed, the
user may write to the GPIO set registers,
PORTxIO_SET
, the GPIO clear
registers,
PORTxIO_CLEAR
, or to the GPIO toggle registers,
PORTxIO_TOGGLE
instead.
While a direct write to a GPIO data register alters all bits in the register,
writes to a GPIO set register can be used to set a single or a few bits only.
No read-modify-write operations are required. The GPIO set registers are
write-1-to-set registers. All 1s contained in the value written to a GPIO set
register sets the respective bits in the GPIO data register. The 0s have no
effect. For example, assume that
PF0
is configured as an output. Writing
0x0001 to the GPIO set register drives a logic 1 on the
PF0
pin without
affecting the state of any other
PFx
pins. The GPIO set registers are typi-
cally also used to generate GPIO interrupts by software. Read operations
from the GPIO set registers return the content of the GPIO data registers.
The GPIO clear registers provide an alternative port to manipulate the
GPIO data registers. While a direct write to a GPIO data register alters all
bits in the register, writes to a GPIO clear register can be used to clear
individual bits only. No read-modify-write operations are required. The
clear registers are write-1-to-clear registers. All 1s contained in the value
written to the GPIO clear register clears the respective bits in the GPIO
data register. The 0s have no effect. For example, assume that
PF4
and
PF5
are configured as outputs. Writing 0x0030 to the
PORTFIO_CLEAR
register
drives a logic 0 on the
PF4
and
PF5
pins without affecting the state of any
other
PFx
pins.
Summary of Contents for EZ-KIT Lite ADSP-BF506F
Page 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Page 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...