UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 141 of 841
NXP Semiconductors
UM10360
Chapter 9: LPC176x/5x General Purpose Input/Output (GPIO)
9.6 GPIO usage notes
9.6.1 Example: An instantaneous output of 0s and 1s on a GPIO port
Solution 1: using 32-bit (word) accessible fast GPIO registers
FIO0MASK = 0xFFFF00FF ;
FIO0PIN = 0x0000A500;
Solution 2: using 16-bit (half-word) accessible fast GPIO registers
FIO0MASKL = 0x00FF;
FIO0PINL = 0xA500;
Solution 3: using 8-bit (byte) accessible fast GPIO registers
FIO0PIN1 = 0xA5;
9.6.2 Writing to FIOSET/FIOCLR vs. FIOPIN
Writing to the FIOSET/FIOCLR registers allow a program to easily change a port’s output
pin(s) to both high and low levels at the same time. When FIOSET or FIOCLR are used,
only pin/bit(s) written with 1 will be changed, while those written as 0 will remain
unaffected.
Writing to the FIOPIN register enables instantaneous output of a desired value on the
parallel GPIO. Data written to the FIOPIN register will affect all pins configured as outputs
on that port: zeroes in the value will produce low level pin outputs and ones in the value
will produce high level pin outputs.
A subset of a port’s pins may be changed by using the FIOMASK register to define which
pins are affected. FIOMASK is set up to contain zeroes in bits corresponding to pins that
will be changed, and ones for all others. Solution 2 from Section 9.6.1
above illustrates
output of 0xA5 on PORT0 pins 15 to 8 while preserving all other PORT0 output pins as
they were before.
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