Beckhoff First Scan Bit Repack May 2026

In Beckhoff’s TwinCAT environment, the First Scan Bit is a fundamental diagnostic tool used to initialize logic, reset variables, or trigger specific startup sequences the moment the PLC transitions from Config/Stop

Logic: 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

Final ResultIn Beckhoff TwinCAT, the First Scan Bit is accessed via the _TaskInfo system array using the FirstCycle property. This bit is uniquely TRUE during the first execution cycle of a task, allowing for precise system initialization.  First Scan Bit - OpenPLC Forum In Beckhoff’s TwinCAT environment, the First Scan Bit

Reset it at the end of your main program:Place this line at the very bottom of your MAIN program or the last task to execute : Highly reliable if implemented at the program's end