I don't understand with this equation(from AN532):
PID equation:

Eu = Eu + u0;

out = (kp*u0) +
      (ki*Eu) +
      (kd*(u0-u1));

the integral error is Eu = Eu + u0, means sum of error,
what if the Eu is overflow and back to zero? is it OK?
it means there is no integral(ki*Eu = 0).

any other equation for PID?

thanks

f