I/O Block
Description
The Watchdog Has Tripped expression indicates the state of the controller's safety system. If tripped then motion is prevented at the hardware level regardless of software commands. Watchdog Has Tripped is a latched condition. One of the conditions that causes the watchdog to trip is firmware inattention. If the real-time operating system supporting the motion application fails to operate properly this hardware tripped condition stops motion. The second cause of a Watchdog Has Tripped condition is the EStop signal not being satisfied. EStop is an input requiring an active, asserted condition to permit motion. If a normally-closed EStop button releases the EStop signal, or if a wire breaks, or an insulation breakdown shorts the wire to a grounded conduit, then the EStop signal will not be satisfied and the hardware shutdown occurs. Restoring motion requires satisfying the EStop signal and using the Reset Watchdog command.
Escapes
If the cause of the watchdog safety system tripping is still present, such as a disable signal remaining active, then the watchdog safety system will fail and generate a Watchdog Failed To Reset escape code.
Examples
This Show As block provides Watchdog Has Tripped status:
This block list, referring to a List Console control, could be used to notice that the watchdog has tripped and recommend a recovery procedure:
Related Topics