Technical information

Tasks
42
EIO0000000638 04/2012
System and Task Watchdogs
Introduction
Two types of watchdog functionality are implemented for the XBT GT/GK HMI
Controller. These are:
z System Watchdogs: These watchdogs are defined in and managed by the
controller OS (firmware). These are not configurable by the user.
z Task Watchdogs: Optional watchdogs that can be defined for each task. These
are managed by your application program and are configurable in SoMachine.
System Watchdogs
The two system watchdogs common to the M2•8 and LMC series controllers for task
overflow detection are not supported by the XBT GT/GK HMI Controller.
NOTE: If an application is sensitive to task time overrun, you should manually set
the Task Watchdog.
Task Watchdogs
SoMachine allows you to configure an optional task watchdog for every task defined
in your application program. (Task watchdogs are sometimes also referred to as
software watchdogs or control timers in the SoMachine online help). When one of
your defined task watchdogs reaches its threshold condition, an application error is
detected and the controller enters the HALT state.
When defining a task watchdog, the following options are available:
z Time: This defines the allowable maximum execution time for a task. When a
task takes longer than this the controller will report a task watchdog exception.
z Sensitivity: The sensitivity field defines the number of task watchdog exceptions
that must occur before the controller detects an application error.
A task watchdog is configured on the Configuration sub-tab of the Task
Configuration tab for the individual task. To access this tab, double-click on the task
in the device tree.
NOTE: For more details on watchdogs, refer to the CoDeSys online help.