Real Time Settings
As a central configuration tool of the TwinCAT System, the TwinCAT System Manager contains below the rubric SYSTEM - Configuration the entry Real-Time Settings. This is where the basic TwinCAT system parameters are specified or changed if necessary.
If this entry is selected, the "Settings" dialog (described below), the "Online" and the "Priorities" dialog (described later) appear on the right-hand side in the System Manager.
”Settings” tab
Base Time
The TwinCAT schedulers change on every tick from Windows to the TwinCAT real time. The planned and necessary task is then performed in TwinCAT real time. By the time the CPU limit (see below) has been reached, the system has changed back to Windows. The TwinCAT basis time is therefore the shortest possible task cycle time. The cycle time can also be a multiple of the basis time. The basis time should only be set to less than a millisecond if necessary and with correspondingly fast PC systems. The following are possible: (none), 1ms, 500µs, 333µs, 250µs, 200µs, 125µs, 100µs, 66µs and 50µs.
TwinCAT can be used without executed real-time by setting the Bse Time value to none, realtime will not be executed. Implementations which don´t need real-time, work as usual (AMS Router, TwinCAT Scope, ADS OCX, ...)
Restricitions:
Real-time tasks, like PLC tasks, software tasks and I/O tasks (Profibus, DeviceNet, Sercos or Lightbus) cannot be executed.
CPU Limit
Specify the CPU percentage proportion that completely fills the TwinCAT real time, the remainder is reserved for Windows (and for surface programs). The value can be set very high since it is automatically reset to Windows when the real time task has completed its cycle.
Fast Tick
Only for special TwinCAT extensions which require a rapid tick irrespective of basis time (e.g. camshaft controller).
Latency Warning
The TwinCAT real time functions on practically all PC systems with extremely low fluctuations (Jitter). These jitters are measured continuously. If a pre-set limit is exceeded, the system can issue a warning.
Router Memory
The TwinCAT Router adminstrates the communcation of all participants. Changes of the memory size will be activ after a reboot.
”Online” tab
The online display gives information about the current CPU load. This is the amount of time required by the real time task. The bright green line indicates the pre-set CPU Limit value.
In addition, the current jitter (system latency time) is given in the bottom window.
Additional info about the History View can be found under: Settings for History View.