Siemens SIMATIC S7-1200 Function Manual page 242

Instructions
9.1 PID_Compact
The Error parameter indicates if an error is pending. When the error is no longer pending,
Error = FALSE. The ErrorBits parameter shows which errors have occurred. Use
ErrorAck to acknowledge the errors and warnings without restarting the controller or
clearing the integral action. Switching operating modes no longer clears errors that are no
longer pending.
You can configure the reaction to error with SetSubstituteOutput and
ActivateRecoverMode.
● Substitute output value
You can configure a substitute output value that is to be output if an error occurs.
● Switching the operating mode
You specify the operating mode at the Mode in/out parameter and use a rising edge at
ModeActivate to start the operating mode. The sRet.i_Mode tag has been omitted.
● Multi-instance capability
You can call up PID_Compact as multi-instance DB. No technology object is created in
this case and no parameter assignment interface or commissioning interface is available.
You must assign parameters for PID_Compact directly in the multi-instance DB and
commission it via a watch table.
● Startup characteristics
The operating mode specified at the Mode parameter is also started on a falling edge at
Reset and during a CPU cold restart, if RunModeByStartup = TRUE.
● ENO characteristics
ENO is set depending on the operating mode.
If State = 0, then ENO = FALSE.
If State ≠ 0, then ENO = TRUE.
● Setpoint value specification during tuning
You configure the permitted fluctuation of the setpoint during tuning at the
CancelTuningLevel tag.
● Value range for output value limits
The value 0.0 no longer has to fall within the output value limits.
● Pre-assigning the integral action
Using the tags IntegralResetMode and OverwriteInitialOutputValue, you can determine
the pre-assignment of the integral action when switching from "Inactive" operating mode
to "Automatic mode".
● Switching a disturbance variable on
You can switch a disturbance variable on at the Disturbance parameter.
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Function Manual, 03/2017, A5E35300227-AC
PID control