Siemens UL1066, UL 489 specifications Exception Responses, Request Message to slave

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Communication-capable Circuit Breakers

WL Circuit Breaker

Exception Responses

Except for broadcast messages, when a master device sends a query to a slave device, it expects a normal response. One of four possible events can occur from the master's query:

1.If the slave device receives the query without a communication error, and can handle the query normally, it returns a normal response.

2.If the slave does not receive the query due to a communication error, no response is returned. The master program will eventually process a timeout condition for the query.

3.If the slave receives the query, but detects a communication error (parity or CRC), no response is returned. The master program will eventually process a timeout condition for the query.

4.If the slave receives the query without a communication error, but cannot handle it (for example, if the request is to read a non-existent coil or register), the slave will return an exception response informing the master of the nature of the error.

The exception response message has two fields that differentiate it from a normal response:

Function Code Field: In a normal response, the slave echoes the function code of the original query in the function code field of the response. All function codes have a most-significant bit (MSB) of 0 (their values are all below 80 hex). In an exception response, the slave sets the MSB of the function code to 1 (adds 80 hex to the function code). With the function code's MSB set, the master's application program can recognize the exception response and can examine the data field for the exception code.

Data Field: In a normal response, the slave may return data or statistics in the data field (any information that was requested in the query). In an exception response, the slave returns an exception code in the data field. This defines the slave condition that caused the exception.

Example:

Request Message to slave

The following is an example of a request to read Dataset 1 (Diagnostic Information) from a COM16 slave device at MODBUS address 7. Dataset 1 has 8 registers, but in this example, the Master tries to read just 6 registers.

07H

Slave Address

03H

Function Code

01H

Register Start Address “High” (Dataset 1

 

address is 0100 hex)

00H

Register Start Address “Low”

00H

Quantity of Registers “High”

06H

Quantity of Registers “Low” (6 registers is not

 

valid)

xxH

CRC Check Code “Low”

xxH

CRC Check Code “High”

Reply Message from slave

The response returns the function code with the high bit set indicating an exception response. The Exception Code returned is 03 (Invalid Data Value). This exception code indicates that an illegal amount of data was specified for the requested Dataset.

07H

Slave Address

83H

Function Code

03H

Exception Code (Illegal Register Amount)

xxH

CRC Check Code “Low”

xxH

CRC Check Code “High”

3/9

WL MODBUS Communication and Electronic Accessories • January 2005

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Contents Powerful ideas Global network of innovationCommunication-capable Circuit Breakers Communication-capable Circuit Breaker Safety Guidelines Qualified PersonnelCorrect Usage Registered TrademarksIntroduction Overview Introduction Content of the ManualGeneral System Solutions WL Circuit Breakers-Modular IntelligentCost Saving Easy PlanningCommunication Bus Systems ModbusCommunication Structure of the WL Circuit Breakers Ethernet WL Circuit Breaker Introduction and Overview Brief Description of the WL Circuit BreakerCubicleBUS Communications Capability of the Electronic Trip Units ETUsFunctional overview of the trip unit system ETU725 ETU727 ETU745Setting range of the Ig Basic Functions ETU725 ETU727 ETU745Basic Functions ETU748 ETU755 ETU776 Communication Data Availability on the CubicleBUS Data point group ETU745Metering Data points with the same source 755 orModbus Module COM16 Pin ConfigurationModbus COM16 Module and the BSS Modbus Write Protection DPWriteEnable Modbus Installation GuidelineCubicleBUS + Data Exchange via the COM16 ModuleMeaning Position and text on the cable CubicleBUS Rear Microswitch S46 Middle S47 Front S48 MeaningCubicle BUS LED Meaning PositionBreaker Status Sensor BSS Metering Function Plus GeneralWaveform buffer Metering Function PlusHarmonic analysis Parameters for the settings of the metering function Voltage TransformersVT Accuracy Maximum distance from voltage transformerMetering range 81THDC Extended Protective Function Important functions/parameters for communicationsLoad Management Normal Positive Power Flow Direction SetpointsMinimum for Communicated Currents Event and Trip LogExternal CubicleBUS Modules Rotary SwitchesInstallation CubicleBUS Installation Guidelines Power SupplyMaximum CubicleBUS Configuration LED Display MeaningCubicleBUS LED Meaning All other LEDs MeaningTesting the Digital Input and Output Modules DeviceTechnical data for the digital input module Digital Input ModuleFunctional description Functional description for changing parameter setsDigital Output Module with Rotary Switch Selector switch position to the leftSelector switch position to the right Delay timeConfigurable Digital Output Module Technical data for the digital configurable output module Trigger event Waveform buffer BPower value ranges W/VA Analog Output ModuleTest function Switch position cosTechnical data for the analog output module Example as illustrated in Graphic ZSI ModuleOperating principle Technical data for the ZSI module It trips after tZSI = 50 ms. Time saved = 250 msCommunication-capable Circuit Breakers General information Output current Inrush current Type Order No Communication-capable Circuit Breakers Modbus Profile for WL Circuit Breaker Supervisory Systems Function 02 Read Discrete Inputs COM16 Supported Function CodesFunction 01 Read Coils Reply Message from slave Function 03 Read Holding RegistersRequest Message to slave Function 07 Read Exception Status Function 04 Read Input RegistersFunction 05 Write Single Coil Function 12 Get Communication Event Log Function 08 DiagnosticsFunction 11 Get Communication Event Counter What the Event Bytes Contain COM16 slave Send EventFunction 15 Write Multiple Coils Function 16 Write Multiple Registers Exception Responses Exception Codes Code Name MeaningBasic Data Type 2 Registers and Default Data Points Default Register ListsBasic Data Type 1 Registers and Default Data Points Basic Data Type 3 Registers and Default Data Points Complete List of Datasets Data bytesSample Dataset Min Max BitsBit Mapping for Breaker Status Register Byte Register DescriptionWL Configurator Brief Description Communication-capable Circuit Breakers Breaker Data Adapter BDA Breaker Data Adapter Plus BDA Plus Benefits of the BDA Brief Description and System RequirementsDescription BDA in Offline Mode or BDA Plus BDA as a Hand-Held Device or BDA PlusBDA Plus as an Ethernet Interface Intranet and InternetGetting started with the BDA Plus What is Java?Circuit breaker requirements Permanent Connection to WL Circuit BreakersTemporary Operation Meaning of the LEDs on the BDATechnical data for the BDA and BDA Plus 4This table provides technical data for the BDA and BDA PlusConnection to the BDA via the Serial Communication System Usually have to be changed. They are shown as a referenceBreaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Breaker Data Adapter BDA Connection to the BDA Plus via the Ethernet Interface Definition of Key TermsIP Addresses Subnet MaskExample BDA IP AddressOperating Instructions and Troubleshooting Offline/Online ModeLanguages and Help Displaying DataPassword Protection SentronOperation Example PrintingTroubleshooting List Fault Description Solution Siemens Energy & Automation, Inc Siemens Energy & Automation, Inc. All Rights Reserved
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