Beckhoff First Scan Bit -

Without a proper first scan routine, your machine might start with actuators in unpredictable positions or unfinished states from a previous run.

bit in Allen-Bradley systems. Instead, you must either access task-specific system information or create a custom flag. Method 1: Using Built-in System Info (Recommended) TwinCAT provides task-specific diagnostics through the array. This contains a FirstCycle boolean that is automatically set to for exactly one scan when the PLC starts or restarts. Structured Text Example:

If you reset the PLC program without a hard power cycle or runtime restart, the behavior depends on whether you have retained the variable. ⚠️ Important Considerations beckhoff first scan bit

Here’s a complete, ready-to-use post explaining the in TwinCAT PLC.

To use this natively, you can reference the global structure _TaskInfo . Below is the industry-standard implementation pattern in Structured Text (ST): Without a proper first scan routine, your machine

(without download) → Counter does not increment (warm start without new program) → In many cases, bFirstScan stays FALSE here unless configured to detect warm starts.

Name the method exactly FB_init . TwinCAT will automatically populate the required input parameters: bInitRetains : BOOL and bInCopyCode : BOOL . Method 1: Using Built-in System Info (Recommended) TwinCAT

The difference between a and a warm start in relation to this bit. Beckhoff CX1010 first scan | PLCtalk - Interactive Q & A