Siemens SIMATIC S7-1200 Function Manual page 364

Instructions
9.2 PID_3Step
State / Re- Description
tain.Mode
4 Manual mode
In manual mode, you specify manual output values in the Manual_UP and Manual_DN parameters or Man-
ualValue parameter. Whether or not the actuator can be moved to the output value in the event of an error
is described in the ErrorBits parameter.
This operating mode is enabled if Retain.Mode = 4, or on a rising edge at ManualEnable.
If ManualEnable changes to TRUE, only State changes. Retain.Mode retains its current value. On a falling
edge at ManualEnable, PID_3Step returns to the previous operating mode.
The switchover to automatic mode is bumpless.
PID_3Step V1.1
Manual mode is always possible in the event of an error.
PID_3Step V1.0
Manual mode is dependent on the ActivateRecoverMode tag in the event of an error.
5 Approach substitute output value
This operating mode is activated in the event of an error or when Reset = TRUE if Errorbehaviour = 1 and
ActivateRecoverMode = FALSE..
PID_3Step moves the actuator to the substitute output value and then switches to "Inactive" mode.
6 Transition time measurement
The time that the motor needs to completely open the valve from the closed condition is determined.
This operating mode is activated when GetTransitTime.Start = TRUE is set.
If endstop signals are used to measure the transition time, the valve will be opened completely from its
current position, closed completely, and opened completely again. If GetTransit-
Time.InvertDirection = TRUE, this behavior is inverted.
If position feedback is used to measure the transition time, the actuator will be moved from its current posi-
tion to a target position.
The output value limits are not taken into consideration during the transition time measurement. The actua-
tor can travel to the high or the low endstop.
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Function Manual, 03/2017, A5E35300227-AC
PID control