第三章MSP430基本外设解读.ppt

P1 端口输入输出电路 input/output schematic P1SEL.x=0，不考虑中断功能 P1SEL.x P1DIR.x P1OUT.x P1IN.x P1.x x = 0 ~ 7 P1SEL.x=0 , P1DIR.x=1 General-purpose digital I/O——Output P1SEL.x=0 , P1DIR.x=0 General-purpose digital I/O——Input Direction Registers PxDIR（输入/输出方向寄存器） Each bit in each PxDIR register selects the direction of the corresponding I/O pin, regardless of the selected function for the pin. PxDIR bits for I/O pins that are selected for other module functions must be set as required by the other function. Bit = 0: The port pin is switched to input direction Bit = 1: The port pin is switched to output direction Input Register PxIN（输入寄存器） Each bit in each PxIN register reflects the value of the input signal at the corresponding I/O pin when the pin is configured as I/O function. Bit = 0: The input is low Bit = 1: The input is high Output Registers PxOUT（输出寄存器） Each bit in each PxOUT register is the value to be output on the corresponding I/O pin when the pin is configured as I/O function and output direction. Bit = 0: The output is low Bit = 1: The output is high Function Select Registers PxSEL（功能选择寄存器） Port pins are often multiplexed with other peripheral module functions. See the device-specific data sheet to determine pin functions. Each PxSEL bit is used to select the pin function ? I/O port or peripheral module function. Bit = 0: I/O Function is selected for the pin Bit = 1: Peripheral module function is selected for the pin PxREN（上拉或下拉电阻使能寄存器） Bit = 0:禁用上拉/下拉电阻 Bit = 1:使能上拉/下拉电阻 PxDS（输出驱动强度寄存器） Bit = 0:低驱动强度 Bit = 1:高驱动强度 例题：流水灯实验 程序 #include msp430x24x.h unsigned int i; void main() { WDTCTL=WDTHOLD+WDTPW; P1DIR=0xff; while(1) { P1OUT=0x01; for(i=50000;i0;i--); P1OUT=0x02; for(i=50000;i0;i--); P1OUT=0x04; for(i=50000;i0;i--); P1OUT=0x08; for(i=50000;i0;i--); P1OUT=0x10; for(i=50000;i0;i--); P1OUT=0x20; for(i=50000;i0;i--); P1OUT=0x40; for(i=50000;i0;i--); P1OUT=0x80; for(i=50000;i0;i--); } } 3.4 定时器 3.4.2 定时器A ◆ 定时器A的特性 ◆ 定时器A的结构