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M340 Troubleshooting Guide

Goals and Symptoms

How to interpret the front panel lights when diagnosing problems with the M340.

Causes and Fixes

Modicon M340 Processor Troubleshooting

  • The Modicon M340 Programmable Automation Controller is a Mid-range automation system providing small size, yet powerful 32-bit processor for demanding OEM machine and industrial process applications. It is programmed using our cross-platform IEC 61131-3 application development software, Unity Pro (v3.0 or higher). The front panel has a series of LEDs that indicate the status of the M340 processor, SD Memory Card, and system communications.

    The Modicon M340 is available in the following models.


    M340 Processors

    BMXP341000 Standard Level 1, 2MB RAM, USB port,

              • 1-communication port: ModBus/Serial, includes 8MB memory card
    BMXP342000 Advanced Level 2 (Performance) for Modicon M340 PLC
          • 1 USB Port for programming
            1 slot for a memory SD-card
            1 communication port: serial link
            Shipped with 1 standard memory SD-card

    BMXP342010 Advanced Level 2, 4MB RAM, USB port,
              • 2-communication ports: ModBus/Serial and CANopen master includes 8MB memory card.

    BMXP342020 Advanced Level 2, 4MB RAM, USB port,
              • 2-communication ports: ModBus/Serial and Ethernet-ModBus/TCP, includes 8MB memory card

    BMXP342030 Advanced Level 2, 4MB RAM, USB port,
              • 2-communication ports: Ethernet-ModBus/TCP and CANopen master includes 8MB memory card.

    Processor Status Displays


    There are several LEDs available on the front panel of each processor, enabling
    rapid diagnosis of the PLC status.

    These LEDs provide information on:

    · PLC functional status
    · The memory card status
    · Communication with the I/O modules
    · Modbus Serial communication
    · Communication on the CANopen network
    · Communication on the Ethernet network


    The following diagrams shows the physical location of the LEDs on the front panel of the BMX P34 processors:

    BMX P34 1000/2000 Processors LEDs

    BMX P34 2020, BMX 2030/20302 Processors

    Table 1 M340 Processor Status and Error indicator display


    Display differences between version 1 and version 2 of the

    BMX P34 20x0x module.

    Searching for Errors Using the Processor Status LEDs


    The status LEDs located on the processor inform the user of the PLCs operating
    mode and any possible errors.
    The errors detected by the PLC concern:

    · circuits which constitute the PLC and/or its modules: internal errors
    · the process driven by the PLC or the process wiring: external errors
    · functioning of the application executed by the PLC: internal or external errors


    Error Detection

    Error detection is performed at startup (autotest) or during operation (which is the
    case for most equipment errors), during exchanges with the modules, or during
    execution of a program instruction.
    Certain "serious" errors require the PLC to be restarted while others are left to the
    user to decide how to proceed depending on the level of application required.
    There are three types of error:

    · non-blocking
    · blocking
    · processor or system

    Blocking Errors


    Blocking errors, caused by the application program, do not cause system errors but
    prohibit execution of the program. When such an error occurs, the PLC stops
    immediately and goes into HALT mode (all tasks are stopped on the current
    instruction). The ERR LED flashes.

    Restarting of the Application After a Blocking Error
    To end this status it is necessary to init the PLC or to set the %S0 bit to 1.
    The application is then in an initial state:
    · The data resumes its initial value.
    · Tasks are stopped at end of cycle.
    · The input image is refreshed.
    · Outputs are controlled in fallback position.
    The RUN command then allows the application to be restarted.

    Blocking Error Diagnosis
    Indication of a blocking error is signaled by the ERR and RUN LEDs flashing on the
    processor front panel.
    The system words %SW126 and %SW127 indicate the address of the instruction
    which caused the blocking error.
    The nature of the error is indicated by the system word %SW125.
    The following table presents the errors signaled by the values of the system word

    M340 Diagnostic information Memory card

    Memory Card Description

    Only Schneider memory cards are compatible with BMX P34 processors.
    Schneider memory cards use Flash technology and do not require a battery. These
    cards can support about 100,000 write/delete cycles (typical).

    The Memory card access LED is located behind the Memory Card Protective Cover.


    CANopen Diagnostics


    BMX NOM 0200 Module Status Display

    LED Indications


    BMX NOE 01x0 Module

    Ethernet LED

    Display differences between Version 1 and version 2 of the BMX NOE 01x0 module.


Legacy KB System (APS) Data: RESL200598 V1.0, Originally authored by MiOB on 11/26/2009, Last Edited by MiOB on 11/26/2009
Related ranges: Modicon M340.
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