Beckhoff First Scan Bit ((free)) < 2026 Release >

| Test Scenario | Method | What to Verify | |---|---|---| | | Power cycle the controller | First scan code runs exactly once | | Warm Start | STOP → RUN from development environment | Custom flags execute if needed | | Program Download | Download without resetting retain variables | Retain-based initialization behavior | | Online Change | Modify code while running | New instances get proper initialization | | Multiple Power Cycles | Cycle power repeatedly | Counters increment correctly |

🚀 Ensures that PID gains, speed limits, or timers start with default "safe" values rather than zeros.

IF _TaskInfo[fbGetCurTaskIndex.index].FirstCycle THEN // Place initialization logic here // Example: Resetting counters or setting default setpoints END_IF Use code with caution. Copied to clipboard : This method utilizes the PlcTaskSystemInfo data structure available in the TwinCAT system. beckhoff first scan bit

: In industrial settings, a first-scan bit is considered essential for resetting retentive memory and ensuring equipment starts in a safe, predictable state. Alternative for Advanced Users

This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later. | Test Scenario | Method | What to

State machines are a staple of PLC programming. Using the first scan bit to set the initial state ensures a predictable and safe start-up.

If you are working on older legacy controllers (such as the Beckhoff CX1010 or CX1020 series) or maintaining an legacy system, you may find the global system array variable explicit: : In industrial settings, a first-scan bit is

found in Allen-Bradley controllers. Instead, developers typically use one of two methods to detect the first scan cycle of a PLC task: a built-in system variable or a manual "home-made" boolean flag. 1. Built-in Method: PlcTaskSystemInfo TwinCAT provides a structured data type called PlcTaskSystemInfo that contains a specific boolean member for this purpose: FirstCycle