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

Description

Resulting Controller State

External Error

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 an expansion module that is not present or not detected, and has not otherwise been declared as an optional module(1).

  • The boot application in non-volatile memory is not the same as the one in RAM.

  • The I/O LED is red ON.

RUNNING with External Error Detected

Or

STOPPED with External Error Detected

Application Error

An application error is detected when improper programming is encountered or when a task watchdog threshold is exceeded.

The ERR LED is red ON.

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 occurs.

The ERR LED is fast flashing RED.

NOTE: There are some system errors that can be managed by runtime and are therefore treated like application errors.

BOOTING → EMPTY

(1) Expansion modules may appear to be absent for any number of reasons, even if the absent I/O module is physically present on the bus. For more information, refer to I/O Configuration General Description.

NOTE: Refer to the Modicon M262 Logic/Motion Controller – System Functions and Variables – System Library Guide for more detailed information on diagnostics.