Bit | Beckhoff First Scan

Version and platform considerations

A first scan bit is a boolean flag that remains TRUE for exactly one execution cycle of the PLC task. After the first logic solve is complete, the bit drops to FALSE and stays there until the PLC is restarted. beckhoff first scan bit

| Do | Don't | |----|-------| | Use FB_FirstScan from Tc2_System | Rely on manual := TRUE flags | | Keep first scan logic short | Put heavy processing inside first scan | | Set outputs to safe defaults | Assume all retentive data is valid | | Combine with Tc2_Standard for consistent behavior | Use first scan for normal logic flow | Version and platform considerations A first scan bit

boolean, which signals the initial task execution, or by creating a custom global variable initialized to TRUE. Alternative methods include utilizing // Call the function block

: 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

fbGetCurTaskIndex(); // Call the function block