Communication to and between input and output devices in an FF bus is controlled, millisecond by millisecond, by the LAS (link active SCHEDULER). The sequence of communication activities, which the LAS manages, is set up by the system engineer during design or commissioning. A TYPICAL configuration tool will allow you to set up a CYCLE time for each CONTROL loop (whether it resides in the host, or in the field devices, or partly in each), and will automatically arrange the required communication paths and schedules.

 Because of the way the LAS works, all cycle times on one bus segment must be FITTED into a basic “macrocycle”. Probably, in most cases, this will also be the overall scan cycle time for control loops on that segment.

Communication to and between input and output devices in an FF bus is controlled, millisecond by millisecond, by the LAS (link active scheduler). The sequence of communication activities, which the LAS manages, is set up by the system engineer during design or commissioning. A typical configuration tool will allow you to set up a cycle time for each control loop (whether it resides in the host, or in the field devices, or partly in each), and will automatically arrange the required communication paths and schedules.

 Because of the way the LAS works, all cycle times on one bus segment must be fitted into a basic “macrocycle”. Probably, in most cases, this will also be the overall scan cycle time for control loops on that segment.