51单片机通过UDN2916驱动双极性两相四线步进电机转动，程序如下。请问怎么算转速。

Question

void motor()

{
//A/
PH1 = 0;
I01 = 0;
I11 = 0; //以最大电流输出

PH2 = 1;
I02 = 1;
I12 = 1; //关闭电流输出

delaydj(rate);

// A/B
PH1 = 0; //PH1为0 A组线圈为反向电流
I01 = 0;
I11 = 0;

PH2 = 1; //PH2为1 B组线圈为正向电流
I02 = 0;
I12 = 0;

delaydj(rate);

//B
PH1 = 1;
I01 = 1;
I11 = 1;

PH2 = 1;
I02 = 0;
I12 = 0;

delaydj(rate);
//AB
PH1 = 1;
I01 = 0;
I11 = 0;

PH2 = 1;
I02 = 0;
I12 = 0;
delaydj(rate);
//A
PH1 = 1;
I01 = 0;
I11 = 0;

PH2 = 0;
I02 = 1;
I12 = 1;

delaydj(rate);
//AB/
PH1 = 1;
I01 = 0;
I11 = 0;

PH2 = 0;
I02 = 0;
I12 = 0;

delaydj(rate);
// B/
PH1 = 0;
I01 = 1;
I11 = 1;

PH2 = 0;
I02 = 0;
I12 = 0;

delaydj(rate);
// A/B/
PH1 = 0;
I01 = 0;
I11 = 0;

PH2 = 0;
I02 = 0;
I12 = 0;

delaydj(rate);

}
/*******************延时函数****************************/
void delaydj(int time)
{
int i,j;

for(j=0; j <= 2; j++)
for(i =0 ; i <=time; i++);
}
51单片机通过UDN2916驱动双极性两相四线步进电机转动，采用半步八拍的运行方式，请问怎么算转速。
步距角为3.75°。晶振频率（时钟频率）12MHz。延时程序rate最大等于160.最小为40.

Answer 1

和时钟原理一样