Beckhoff First Scan Bit Exclusive May 2026

Ensuring your sequences (SFC) start at "Step 0."

If you use the manual variable method, ensure the line bFirstScan := FALSE; is at the very bottom of your MAIN task. If you put it in a sub-function, other parts of your program might miss the "True" state. beckhoff first scan bit

Use the first scan to ensure all physical outputs are in a "Safe/Off" state before the logic takes over. Ensuring your sequences (SFC) start at "Step 0

Most TwinCAT developers create a global boolean variable and set it to TRUE by default. At the very end of their main program, they set it to FALSE . VAR_GLOBAL bFirstScan : BOOL := TRUE; END_VAR Use code with caution. Main Logic (MAIN PRG): ensure the line bFirstScan := FALSE