Scan Bit - Beckhoff First

// Implementation fbFirstScan(CLK := bInit); bFirstScan := fbFirstScan.Q; bInit := FALSE;

The most straightforward way is to declare a global variable that resets itself after the first cycle. beckhoff first scan bit

But this is still a workaround. The most professional method in Tc3_Standard is to use the StandardLib (from Beckhoff Automation) which includes FB_FirstScan directly. // Implementation fbFirstScan(CLK := bInit)

If you are using Function Blocks, TwinCAT 3 supports the FB_init method. This is a specialized sub-method that runs when the block is instantiated (during PLC startup or after a download), making it the cleanest way to handle block-specific initializations. Why use a First Scan Bit? bFirstScan := fbFirstScan.Q

: Ensures equipment begins in a safe, known state.