Beckhoff — First Scan Bit [repack]

To use this, you must first identify the index of the task currently running your code using the GETCURTASKINDEX function block:

A common alternative for simple applications is to create a "latching" bit that initializes to FALSE and is set to TRUE at the end of the first cycle. This method is highly portable and works across all IEC 61131-3 compliant platforms. beckhoff first scan bit

The is not merely a legacy feature; it is the cornerstone of deterministic machine initialization. By using the Tc2_System.bInit flag or the FB_init method, you separate the chaos of "run-time" from the stability of "start-up." To use this, you must first identify the

_FIRSTSCAN is global but evaluated per task. A faster task might run multiple times before a slower task sees its first scan. : Use task-local first scan if needed, or synchronize via a global flag. By using the Tc2_System

The is a system-generated boolean variable (or memory flag) that is TRUE for exactly one PLC cycle, and FALSE for every subsequent cycle thereafter.