Beckhoff First Scan Bit Jun 2026

The most reliable way to detect the first scan in TwinCAT 3 is to use the structure . Every task has an associated system structure that includes a FirstCycle boolean . Example Implementation (Structured Text):

The First Scan Bit is the "ignition switch" of a TwinCAT program. By isolating startup logic into this single-cycle window, engineers ensure that the system begins its operation from a known, predictable state beckhoff first scan bit

// First scan detection IF bFirstScan AND NOT bFirstScanDone THEN bFirstScanDone := TRUE; // First scan logic here END_IF The most reliable way to detect the first

You can access this feature through the implicit array, which contains data for every task running in your PLC project. Syntax (Structured Text): beckhoff first scan bit