MSP430 PIN Operation Register

1. P port register:

   (1) PxDIR Input/Output Direction Register

            (0: Input mode 1: Output mode)

   (2) PxIN input register

           The input register is a read-only register. The user cannot write to it. The input signal of the I/O port can only be known by reading the contents of the register.

   (3) PxOUT output register

          The contents of the registers are not affected by pin direction changes.

   (4) PxIFG interrupt flag register

            (0: No interrupt request 1: Interrupt request)

            This register has 8 flag bits, corresponding to whether the corresponding pin has a pending interrupt request;

            These 8 interrupt flags share one interrupt vector. The interrupt flags will not be reset automatically and must be reset by software.

            The time of the external interrupt event must be greater than or equal to 1.5 times the MCLK time to ensure that the interrupt request is accepted;

   (5) PxIES interrupt trigger edge selection register

           (0: rising edge interrupt 1: falling edge interrupt)

   (6) PxSEL function selection register

           (0: Select pin as I/O port 1: Select pin as peripheral module function)

   (7) PxREN pull-up/pull-down resistor enable register

           (0: Disable 1: Enable)

(1) All P ports can be used as general IO ports

(2) All P ports can perform byte operations and bit operations

                Byte-wise operations:

                 Example: P1DIR=0xff; //Use P1 port as output port

                                  PIOUT=0x20; //P1 port output 0x20

                                  P1DIR=0x00; //Use P1 port as input port

                                  data=P1IN //Read the external input value of P1 port

                Bitwise operations:

                 Example: P1DIR=BIT0; //Use P1.0 as output port

                            P1OUT|=BIT0; //P1.0 output 1

                            P1OUT&=~BIT0; //P1.0 output 0

                            P1DIR&=~BIT0 //Use P1.0 as input

                            data=P1IN&BIT0 //Read the external input value of P1.0 port