Generating Variable Baud Rate in Modes 1 and 3. In Modes 1 and 3, the Timer 1 overflow rate is used to generate baud rates. If Timer 1 is configured at auto in auto-reload mode to establish a baud rate, the following equation is useful: Baud Rate =2^SMOD × fosc/(32 × 12 ×(256 - th1)). th1=256-(2^smod)/(32*12*baud rate) 那么问题的症结应该在于smod的取值,如一楼所取smod=0的话,则一楼公式应该是对的.而smod=1时应该是版主二楼公式.而在很多资料中只是写到smod对模式2的影响. 不确定smod对方式1,3的影响是不是如我所认为的.我掌握的知识不好,希望版主指点.