FUNCTION_BLOCK "FB1_PLC Cycle Time"

TITLE = PLC Cycle Time

{ S7_Optimized_Access := 'TRUE' }

AUTHOR : 'A.Mol'

VERSION : 1.0

VAR

TimePrevCycle : UDInt;

TimeCurrentCycle : UDInt;

CPU_CycleTime_ns : UDInt;

CPU_CycleTime_s : Real;

CalculationExecuted : Bool;

END_VAR

VAR_TEMP

OneCycleBit : Bool;

END_VAR

BEGIN

(******************************************************************************************************************************

Title           : FB_CPU Cycle Time

Date Created    : 18-04-2017

Author          : A.Mol

Functional Description:

This Function Block calculates the last CPU's cycle time. This due to the lack of "OB1_PREV_CYCLE" at the S7-1200 CPU.

Each cycle the current CPU time (nanosecond part) is subtracted from the CPU time written in the previous cycle.

Needs       : RD_SYS_T in OB1 written to DB(100)

Revision info:

V1.0    18-04-2017  AMO: - Original created version.

******************************************************************************************************************************)

// Initialize =================================================================================================================

#OneCycleBit := TRUE;

#CalculationExecuted := FALSE;

// CPU Cycle Time Calculation =================================================================================================

(* Writing the current time to a local variable *)

IF #OneCycleBit

THEN

#TimeCurrentCycle := "DB100_PLC Info".DateTime.NANOSECOND;

END_IF;

(* Compare if the current time is greater than the last written time. If so, subtract both *)

IF #TimeCurrentCycle > #TimePrevCycle

THEN

#CPU_CycleTime_ns := #TimeCurrentCycle - #TimePrevCycle;

#CalculationExecuted := TRUE;

END_IF;

(* If the calculation has been executed, write the current time to the previous time *)

IF #CalculationExecuted

THEN

#TimePrevCycle := #TimeCurrentCycle;

END_IF;

(* Convert the nanosecond time to a decimal second time *)

#CPU_CycleTime_s := UDINT_TO_REAL(#CPU_CycleTime_ns) / 1.0e9;

END_FUNCTION_BLOCK