1、数字I/O模块概述
MSP430拥有12组数字I/O端口，为P1到P11和PJ，每个端口8位。可按位设置输入输出、片内上下拉及外设复用模式。P1和P2具有中断功能，可设置中断脉冲沿类型。
2、数字I/O模块寄存器设置
①PxIN(Input Registers)
Bit=0:Input is low
Bit=1:Input is high
②PxOUT(Output Registers)
When configured as I/O function, OUTPUT direction.
Bit=0:Output is low
Bit=1:Output is high
When configured as I/O function, INPUT direction and the Pullup/Pulldown resistor is enabled.
Bit=0:Pin is pulled down
Bit=1:Pin is pulled up
③PxDIR(Direction Registers)
Bit=0:Port pin is switched to input direction
Bit=1:Port pin is switched to output direction
④PxREN(Pullup or Pulldown Resistor Enable Registers)
Bit=0:Pullup/pulldown resistor disabled
Bit=1:Pullup/pulldown resistor enabled
⑤PxDS(Output Drive Strength Registers)
Bit=0:Reduced drive strength
Bit=1:Full drive strength
⑥PxSEL(Function Select Registers)
Bit=0:I/O Function is selected for the pin
Bit=1:Peripheral module is selected for the pin
Warnin:Setting PxSEL does not automatically set the pin direction.
3、中断端口P1，P2相关寄存器
①PxIFG(Interrupt Flag)
Bit=0:No interrupt is pending
Bit=1:An interrupt is pending
Warning:MSP430为边沿触发中断
②PxIES(Interrupt Edge Select Registers)
Bit=0:Respective PxIFG flag is set with a low-to-high transtion
Bit=1:Respective PxIFG flag is set with a high-to-low transtion
③PxIE(Interrupt Enable Registers)
Bit=0:The Interrupt is disabled
Bit=1:The Interrupt is enabled
④PxIV(Interrupt Vector) 16位