Beckhoff First Scan Bit

: If your project has multiple PLC tasks, _AppInfo.bFirstCycle is local to the context of the task it is called in.

// Main logic uses bIsFirstScan... // Final line of code: bIsFirstScan := FALSE; Use code with caution. Copied to clipboard 3. SFC Initialization Flag beckhoff first scan bit

However, for standard ladder logic or structured text programs, the boolean flag method above is the industry standard for Beckhoff systems. : If your project has multiple PLC tasks, _AppInfo

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 Copied to clipboard 3

// 2. Clear alarms GVL.stAlarmBuffer := (Count := 0);

⚠️ Always use the first scan bit to put your machine into a Safe State . Never assume the hardware is in the same position it was when the power went out.

VAR_GLOBAL bIsFirstScan : BOOL := TRUE; // Starts TRUE when the PLC runtime begins END_VAR Use code with caution. Copied to clipboard