How to a first-scan bit if you're using an older version of TwinCAT.
During the very first scan, some hardware modules, fieldbus nodes (EtherCAT distributed clocks), or pointers linked via ADR() might still be establishing stable states. Avoid deep pointer referencing or complex string manipulations inside the first scan block unless you have explicitly verified that memory handles are valid. 2. Keep Axis Initialization Sequential beckhoff first scan bit
IF _TaskInfo[1].bFirstCycle THEN // Logic here only runs once InitialSetpoint := 50.0; SystemReady := FALSE; END_IF Use code with caution. Copied to clipboard Best Practices and Pitfalls The primary risk with first scan logic is dependency loops How to a first-scan bit if you're using
If you are used to pure IEC 61131-3 logic or want something simple that does not require checking task arrays, you can use variable initialization. IF TwinCAT_SystemInfoVarList
IF TwinCAT_SystemInfoVarList._TaskInfo[1].CycleCount = 1 THEN // Execute first scan logic END_IF; Use code with caution.