Two types of watchdog functionality are implemented for the Magelis SCU HMI Controller:
oTask Watchdogs: These watchdogs are optional watchdogs that you can define for each task. These are managed by your application program and are configurable in SoMachine.
oHardware Watchdogs: This watchdog is managed by the HMI controller main CPU. It is not configurable by the user.
NOTE: Infinite loops are not interrupted if a user does not set the Task Watchdog manually.
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:
oTime: 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.
oSensitivity: The sensitivity field defines the number of task watchdog exceptions that must occur before the controller detects an application error.
To access the configuration of a task watchdog, double-click the Task in the Applications tree.
NOTE: For more information on watchdogs, refer to SoMachine Programming Guide.
If the main CPU of an HMISCU processes invalid instructions (application corruption or invalid commands) or does not respond for 10 seconds, the Hardware Watchdog is triggered. This results in a software reset of the Vijeo Designer Runtime. After the reset, no controller application is loaded and the Vijeo Designer is in a Ready for Download state.
A new HMI and Controller application must be downloaded to the device to recover it from this condition.
