SAF task

The block execution task (SAF task) directly executes commands that do not require preprocessing or have been prepared by the SVB task and handles cyclic communication with the drive devices.

• motion commands of the Tc2_MC2 library, like MC_MoveAbsolute, MC_MoveRelative, MC_MoveVeloctiy etc.
• coupling axes
• cyclic setpoint generation for all axes and output to drives
• cyclic acquisition of the actual position and position control, if not directly controlled by the drive
• I/O communication, e.g. for the evaluation of latch positions

Task tab

The SAF task is configured via the NC/PTP NCI Configuration node below the MOTION node, which is called NC-Task 1 SAF by default. Details about the task dialog, see TE1000 | The TwinCAT Project.

High Prio ADS commands

As of TwinCAT 3.1 Build 4026, ADS communication takes place at the start of an SAF task cycle by default. This corresponds to a higher prioritization of ADS communication.

Up to and including TwinCAT 3.1 Build 4024, ADS communication takes place at the end of an SAF task cycle. By unchecking High Prio ADS commands, ADS communication also takes place on a TwinCAT 3.1 Build 4026 system at the end of an SAF task cycle.

Settings tab

Retain data

TwinCAT-NC uses retain data to restore the position of individual axes with absolute measured value system at system startup. The Retain setting determines globally whether data required for this purpose is saved when the system is stopped and loaded when the system is started. In addition, the storage must be parameterized for each axis that requires such data (see Data Persistence).

• None: No retain data is saved or loaded.
• Store only: No retain data is loaded at system startup. Retain data is saved when the system is stopped. This setting is only used for compatibility with old configurations.
• Load/Store: Retain data is stored at system stop and loaded at system start. If there is no data or only corrupt data at system startup, the system aborts the startup process with an error.
  The system cannot be started in this mode when the retain data is configured for the first time, so the Mode Load (if available)/Store should be set first and then reset to Load/Store after a successful system start.
• Load (if available)/Store: Retain data is stored at system stop and loaded at system start. If there is no data or only corrupt data at system startup, the system starts without retain data.
  Axes that rely on retain data are in the "not referenced" state. The application should check this state and take action.

Symbol Names

The setting Symbol Names, Language independent specifies that the generic part of the symbol name is not changed. This is then always held in English.

For example, without this setting Axes.Axis 1.SetPos would change to Achsen.Axis 1.SetPos when switching language from English to German, while with the setting it would remain English.

Online tab

The Online tab shows the utilization of the task over time and indicates the number of cycle time overruns. Details can be found in the TE1000 | TwinCAT 3 XAE documentation.