Beckhoff First Scan Bit |best| ⭐ Best Pick

// Reset the flag after first cycle IF bFirstScanDone THEN bFirstScan := FALSE; END_IF

(* Logic Section ) IF bFirstScan THEN ( --- This runs ONLY on the first scan --- ) nCounter := 0; ( Reset variables ) ( Perform other startup routines *)

: Place code at the very end of your main program that sets this bit to FALSE . Because the variable is initialized to TRUE , it remains so for the entire first scan before being permanently toggled off. Comparison and Review PlcTaskSystemInfo.FirstCycle Manual Custom Bit Reliability Native to TwinCAT; handles task-specific restarts. Highly reliable if implemented at the program's end. Complexity Requires calling GETCURTASKINDEX . Extremely simple to declare and use. Best Use Case beckhoff first scan bit

BEGIN IF FirstScan THEN // Execute initialization code here // e.g., set default values, initialize variables FirstScan := FALSE; END_IF

: Use bInit in FB_Init – it respects online changes differently. Or explicitly handle a "reinit" via a variable that you toggle manually. // Reset the flag after first cycle IF

Edge-detected approach

PROGRAM MAIN VAR bFirstScan : BOOL; rst : BOOL; END_VAR Highly reliable if implemented at the program's end

Note: exact symbol names can vary by TwinCAT version and project conventions.