This register is used to produce a HIGH level output at the port pins configured as GPIO in an OUTPUT mode. This feature should be used carefully in an application since it affects the entire port. Writing to the IOPIN register stores the value in the port output register, bypassing the need to use both the IOSET and IOCLR registers to obtain the entire written value. In that case, the pin value read in the IOPIN register is not valid. Selecting the pin as an A/D input disconnects the digital features of the pin. If a pin has an analog function as one of its options, the pin state cannot be read if the analog configuration is selected. Any configuration of that pin will allow its current logic state to be read from the IOPIN register. As an example, a particular port pin may have GPIO input, GPIO output, UART receive, and PWM output as selectable functions. The register will give the logic value of the pin regardless of whether the pin is configured for input or output, or as GPIO or an alternate digital function. This register provides the value of port pins that are configured to perform only digital functions. PORT0 and PORT1 are controlled via two groups of 4 registers. PORT1 has up to 16 pins available for GPIO functions. A total of 30 input/output and a single output only pinout of 32 pins are available on PORT0. LPC/6/8 has two 32-bit General Purpose I/O ports.
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