本帖最后由 yuanhaididai 于 2012-8-9 18:13 编辑
1.In order to reduce the likelihood of the crosstalk between theadjacent signals,RS232 limits the maximum slew rate 30V/μs;
2.The impedance between thedriver and the receiver was defined,the load seen by driver is 3k~7kohm;
3.The standard specifies the capacitive load of the 2500pF.
以上3点是232标准的3个重要指标,第1的意思应该是信号在上升或者下降沿的过渡区的斜率最大不能超过30v/μs,否则信号间的串扰会加大;从第3点可以知道标准规定了驱动器的负载线电容最大不能超过2500pF说明传输电缆不能太长,否则容易引起数据错误,因为随着电缆增长,线电容将增大;第2点说驱动器到接收器间的阻抗为3K~7K,要怎么理解者点好呢? |