Diagnostics data within the Modbus network should be interpreted in a hierarchical manner. The Modbus Network presents diagnostics for all devices and points beneath it, while each individual device displays diagnostics for itself, as well as for its associated register groups and points.
This hierarchical structure means that "Sent Messages" and "Error Counters" are aggregated at each level. For instance, the "Sent Messages" property of a device represents the total number of requests generated by the device itself (such as online polls) in addition to those from each of its owned points and register groups.
The "Status" indicator for the Network, Device, or Point reflects the most critical issue encountered within that context. For example, if a device experiences errors with two points—one due to misconfiguration (Point Modbus Error) and the other related to performance (Point Performance Issue)—the device status will display "Point Modbus Error," referencing the misconfigured point. This prioritization highlights the most severe issue that requires attention.
For a comprehensive overview of system health and size, users can navigate to: /System/Modules/ModbusPlugIn/Diagnostics, which provides insights into the overall state of the system.
Status Values
The possible status values for the status field in Modbus diagnostics are:
Tabelle: Status Values for the Status Field in Modbus Diagnostics
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Values
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Text
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Description
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0
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Ok
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1
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Unknown
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2
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Disabled
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3
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Inefficient Group
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The register group may benefit from reorganization to enhance performance. For example, ensure that all registers within a close address range (e.g., <100) can be read contiguously. If contiguous reading is not feasible, consider splitting the register group so that each subset of registers can be accessed in a single Modbus request.
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4
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Point Performance Issue
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The point cannot be read as quickly as required by the user or system. For instance, if the requested polling rate is 1000 ms but the point only updates every 2000 ms, performance may be impacted.
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5
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Point Network Error
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The most recent attempt to read the Modbus point was unsuccessful due to a network error.
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6
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Misconfigured Group
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A register group contains at least one point that cannot be accessed because of a Modbus error. For example, if there is an attempt to read register 101, but the device lacks this register, it will respond with an error indicating its absence.
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7
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Point Modbus Error
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A point is incorrectly configured and cannot be read. For instance, if there is an attempt to read register 101 and the device does not support it, an error will be generated.
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8
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Invalid Device
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A configuration setting on the device is invalid, preventing successful communication.
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9
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Offline
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Offline
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Hinweis
Errors are categorized according to their severity levels. For example, if a device has one object with a status level of 3 (Inefficient Group) and another object with a status level of 5 (Point Network Error), the device status will reflect the more severe status of 5 (Point Network Error). This approach assists users in identifying and addressing the most critical issues first.
Modbus Error Field
The Modbus error field displays the error code corresponding to the most recent communication failure that resulted in a Modbus error. A Modbus error indicates that a reply was received from the specified device containing an error code as defined in the Modbus standard. These codes are detailed in the Modbus standard documentation: (https://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf) under the section titled "7 MODBUS Exception Responses." It is important to note that this field specifically presents Modbus exception codes rather than general errors.
Network Error Field
The network error field is populated when the most recent error is attributed to a network issue. This includes situations where no response is received from a device or when the received response cannot be accurately decoded.
Unlike the Status and Modbus Error fields, this field does not correspond to a defined data set. Descriptive error messages are generated within the code. Relevant messages are displayed from the operating system framework or Boost communication framework when available to assist with error diagnostics.
Generally, these errors arise when a device or gateway is unresponsive, or when a connection fails due to network conditions (e.g., an unplugged cable or an unreachable device IP address).
In general, if an error message is unclear, the EBO tracelog can provide more data. The error timestamp, which is also part of the diagnostics tab, should be used to find the proper log entries, if any.
Serial communication
errors
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Error message
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Description
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Serial Port Communication Error
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An issue has occurred with communication on the serial port. This could be due to a port initialization failure, read error from the driver, or similar factors. Further details may be available in the log at the timestamp indicated in the "last error" field.
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Operation Not Handled
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A message was processed, but no response data was returned. This indicates an internal error; please refer to the log for additional details. Invalid ID Address – A request was received for a serial device with an invalid ID. Communication will not proceed until the device ID is corrected.
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Message Too Short/Long
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This error arises when the received serial response has an unexpected length. For example, if the header indicates 10 bytes of data, but only 8 or 12 bytes are received.
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Request Stuck Too Long
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The device did not respond within the allotted timeout period. This may indicate a performance issue or that the device is completely offline (e.g., due to a power failure).
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TCP Communication errors
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Error message
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Description
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TCP Device Currently Shutting Down. No Open Connection
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This error occurs when the connection is in the process of shutting down, either during a shutdown/disable action or while restarting the connection due to timeouts.
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Network Operation Timed Out
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This error indicates that the device did not respond in the expected timeframe, which may be due to performance issues or an offline device.
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Boost Errors
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These are not literal errors but refer to specific issues from the Boost TCP implementation. An exhaustive list is not currently available, but the trace log may provide more insight at the error timestamp.
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Connection Terminated
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This error is shown when queued messages are abruptly terminated due to a critical communication error, such as the target device shutting down the TCP connection or the connection being terminated due to a timeout.
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Failed to Find Existing or Create New Modbus Device for $ID
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This error occurs when a TCP connection cannot be established or queued for the specified device with Modbus ID $ID.
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Request Already in Queue
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This error arises when an attempt is made to send a request that exactly matches one already in the device queue. This can occur with long timeouts or if two users are accessing the same Modbus point from different workstations. No Such Priority – This is an internal error that should be reported as a software bug.
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General errors
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Error message
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Description
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Device Address is Invalid or Device is Disabled
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This error occurs if a user tries to read data from a device that is either disabled or has an invalid address.
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Device is Disconnected from Internal Modbus Network
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This indicates an internal error and should be reported as a software bug.
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Attempt to Add Object to Register Group with Invalid Read Code
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Modbus register groups only support read codes for reading Coils and Registers. Points with more complex read codes are not supported in register groups.
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Register Group is Disconnected from Internal Modbus Device
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This indicates an internal error and is considered a software bug.
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Response Data Length or Format Error
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This occurs when bad data is received from the Modbus device.
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Wrong Data Length Scattered Read
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This indicates a data format error or the reception of data specific to a scattered read.
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Modbus Overview