Controller States and Behaviors
Error Detection, Types, and Management
Error Management
The controller detects and manages three types of errors:
External errors
Application errors
System errors
This table describes the types of errors that may be detected:
Type of Error
Detected
External Error
Description
External errors are detected by the system while RUNNING or
STOPPED but do not affect the ongoing controller state. An external error is detected in the following cases:
A connected device reports an error to the controller.
The controller detects an error with an external device, for example, when the external device is communicating but not properly configured for use with the controller.
The controller detects an error with an output.
The controller detects a communication interruption with a device.
The controller is configured for a module that is not present or not detected.
The boot application in Flash memory is not the same as the one in RAM.
Application Error An application error is detected when improper programming is encountered or when a task watchdog threshold is exceeded.
Resulting Controller
State
RUNNING with
External Error
Detected
Or
STOPPED with
External Error
Detected
HALT
System Error A system error is detected when the controller enters a condition that cannot be managed during runtime. Most such conditions result from firmware or hardware exceptions, but there are some cases when incorrect programming can result in the detection of a system error, for example, when attempting to write to memory that was reserved during runtime, or when a system watchdog time-out occurs.
NOTE: There are some system errors that can be managed by runtime and are therefore treated like application errors.
BOOTING → EMPTY
NOTE: Refer to the M258 PLCSystem library Guide for more detailed information on diagnostics.
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