帮朋友写的一个用MCS

代码说明：

帮朋友写的一个用MCS-51的IO口模拟PWM使外接LED亮度渐变的程序，虽然程序小，不过注释清楚，并已调试OK。-written for a friend with a MCS-51 simulation of the IO mouth so that external PWM LED brightness gradual process Although procedures for small, but clearly Notes, and debugging OK.