Sync/Freeze functionality

Sync is used for the simultaneous outputting of outputs for several slaves, Freeze is used for reading in inputs from several slaves simultaneously.

The sequence in TwinCAT with FC310x / EL6731 and Bus Couplers (in K-bus synchronous mode) would therefore be as follows (see section Synchronization):

• The outputs are written at the beginning (I/O at the start of the task) or the end (I/O not at the start of the task) of the task cycle
• This will start the PROFIBUS cycle
• A Sync/Freeze telegram is sent at the start of the PROFIBUS cycle
• This will cause the Bus Couplers to start a K-Bus cycle with the outputs from the last task cycle and transfer the inputs from the last K-Bus cycle
• The master will then send the current outputs to each slave and pick up the transferred inputs
• The inputs are read at the start of the next task cycle
• etc.

Outputs and inputs are therefore always one cycle old.

On the FC310x/EL6731, set the Operation Mode on the "FC310x" or "EL6731" (for TwinCAT) tab of the master to "DP/MC (equidistant)". At the boxes to be operated via Sync/Freeze, click the checkbox Sync/Freeze enable on the slave's Profibus tab. The master always uses group 1 for the Sync/Freeze synchronization.