Beckhoff First Scan Bit 〈1080p 2027〉

In 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

When a PLC starts, variables often default to zero or their last persisted state. However, many industrial systems require a specific "safe state" or initial configuration before the main control loop takes over. The first scan bit acts as a system trigger , allowing programmers to: Set Initial Values: beckhoff first scan bit

// -- Main control loop -- RunMachineLogic(); In Beckhoff TwinCAT, the First Scan Bit is

IF FirstScan THEN IF bInit_Cold THEN // Full factory reset ELSIF bInit_Warm THEN // Restore retain variables, but reinit comms END_IF END_IF In Beckhoff TwinCAT