In automatic mode, the control output Y is determined through the discrete PID closed-loop control algorithm subject to controlled variable PV and reference variable SP. The control output is limited by YMAX and YMIN. The control limits are also limits for the Anti-windup reset.

The changeover from automatic to manual is normally not bumpless, since output Y can take on any value between YMAX and YMIN, and Y goes directly to YMAN at the changeover.

If the changeover from automatic to manual is to be bumpless in spite of this, there are two exemplary possibilities shown for a PID1 Controller.

In manual mode the manually manipulated value YMAN is passed on directly to the control output Y. The control output is, however, limited by YMAX and YMIN. Internal variables will be manipulated in such a manner that the controller changeover from manual to automatic (with I component enabled) can be bumpless. The control limits are also limits for the Anti-windup reset.

In this operating mode the D component is automatically set to 0.

In halt mode the control output remains unchanged; the function block does not influence the control output Y, i.e. Y = Y(old). Internal variables will be manipulated in such a manner that the component sum corresponds to the control output, thus allowing the controller to be driven smoothly from its current position (when the I component is enabled). The control limits are also limits for the Anti-windup reset.

In this operating mode the D component is automatically set to 0.