Chapter4 数字I/O模块

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