In automatic mode, the manipulated variable Y is determined through the discrete PID closed-loop control algorithm subject to controlled variable X and reference variable SP.

In cascade mode, the manipulated variable Y is determined through the discrete PID closed-loop control algorithm subject to controlled variable X and reference variable SP_CAS.

The distinction between these two operating modes, automatic and cascade, is only external in their different use of the reference variable SP. SP_CAS refers to cascade, SP to all other operating modes (with velocity limit). The SP_CAS variable is an input in cascade mode only, in all other modes it is an output. In SP_CAS, the X variable is returned to the master controller when in the modes reset, manual, halt or automatic as well as during startup, permitting bumpless switching from, for instance, fixed setpoint control to cascade control.

In both operating modes, the manipulated variable Y is limited by ymax and ymin. The control limits for the anti-windup measure can be extended using the parameter delt_aw.

In manual mode, the manual manipulated value YMAN is transferred to the manipulated variable Y with a velocity limiter. The manipulated variable Y is set to the YMAN parameter value in ramp form using the velocity (unit 1/s) rate set in the parameter rate_man.

The amount will be evaluated for parameter rate_man. The function of the velocity limiter for YMAN is disabled if rate_man = 0. YMAN is transferred directly to the manipulated variable. The manipulated variable is 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 Anti-windup measure is designed just like in automatic mode.

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

In Reset mode, the reset value YRESET is transferred directly to the manipulated variable Y. The manipulated variable is 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 Anti-windup measure is performed just like in automatic mode.

In halt mode, the control output remains as is, i.e. the function block does not change the manipulated variable Y. Internal variables will be manipulated in such a manner that the controller can be driven smoothly from it's current position. Manipulated variable limits and Anti-windup measures are as those in automatic mode. Halt mode is also useful in allowing an external operator device to adjust control output Y, whereby the controller's internal components are given the chance to continuously react to the external influence.

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

The definition of non-bumpless operation is when the controller exhibits a jump during operating mode switchover (e.g. manual to automatic) due to the P component in the manipulated variable Y. Depending on the controller's area of utilization, it might be useful for the controller to make a jump-type correction of the manipulated variable when switching over, for instance from manual to automatic, provided the system deviation is not equal to 0.

The definition of bumpless operation is, the controller does not produce a discontinuity in the manipulated variable Y during an operating mode switchover. That is, it should continue at exactly the same location where it was positioned last. In this operating mode, the internal I component is corrected by the P contribution. If no I component is enabled, bumpless operation is achieved by tracing the operating point OFF such that the controller can continue during operating mode change without a bump in spite of system deviation being not equal to 0.