1 a practical guide to device integration with an emphasis on the modbus serial protocol device...

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A Practical Guide to Device Integration with an emphasis on the Modbus Serial Protocol

Device IntegrationDevice Integration

Goals for this Presentation

Provide information on the steps required for successful device integration implementation.

Provide information for making decisions for selecting the proper hardware and software for the implementation.

Provide information on the types of tools that are useful for a successful implementation.

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What you should know before you start

Steps to successfully implement a device interface

Information on the Device to be integrated.

I/A Series products: How to choose the appropriate Hardware/Software

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Integration EngineeringIntegration Engineering

Definition Design Implement

Integrate Start-up

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Integration Definition – Foreign Device Definition ManufacturerModelCommunications Protocol SupportedTypes of ports availableDecide on Communication parametersDecide on Network AddressTypes of Queries supportedMemory Map of desired data pointsDoes the device have a user mappable memory range?Does the device have redundant communications capability?How many devices will be on this serial bus?How far away from the integrator will the device be?

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Integration Definition – Foreign Device DefinitionManufacturerModel

This is not necessarily essential information, but you may want to use some aspect of the manufacturer/Model information to name your ECB, Compound, or Control Blocks.

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Integration Information – Foreign Device DefinitionCommunications Protocol Supported

I/A Series Integration Information

An MG30 supports Modbus Master RTU ProtocolAn FBM224 Supports Modbus Master RTU ProtocolAn AB30 Supports Allen-Bradley DF1 protocolAll other protocols require the use of the DI30 with a protocol specific software component

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Integration Definition – Foreign Device DefinitionTypes of ports available

What type of physical connector does the device have?DB9, DB25, RJ45, Terminal Strip, Male or Female

Which serial protocols are supported?RS232, RS485, RS422Note: RS485 is the only multi-drop protocol.

I/A Series Integration InformationAll 30 Series integrators support RS232 with a Male 25-pin D-connector.The FBM224 supports RS232 with a male 25-pin D-connector ANDRS485/RS422 with terminal connections.

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Integration Definition – Foreign Device DefinitionDecide on Communication parameters

Baud Rate (Typically 9600 default)Databits (7 or 8)Parity (Even, Odd, None)Stop Bits (1 or 2)

I/A Series Integrator Information

Integrators support up to 19200 Baud (configurable)

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Integration Definition – Foreign Device IntegrationDecide on Network Address

This network address is specific to the protocol

Modbus Specific InformationThe valid network address range for Modbus is between 1 and 256.0 is a broadcast address.The Master does not have a specified address (only one master per bus). If more than one device exists on the serial bus, each must have a unique network address.

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Integration Definition – Foreign Device DefinitionTypes of Queries supported

Modbus Specific Information

Typically function codes 1,2,3,4,5,6,15,and 16 are supported by modbus devices

Heartbeat is one query type for Modbus (function code 8) that can cause intermittent failures if the field device does not support this function.

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Integration Definition – Foreign Device DefinitionMemory Map of desired data points

Modbus Specific Information

The Memory Address and whether the query is a read or a write determines function code used to obtain that information.

Memory Map Read Write0-9999 function code 1 function code 5,1510000-19999 function code 2 N/A40000-49999 function code 3 function code 6, 1630000-39999 function code 4 N/A

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Integration Definition – Foreign Device DefinitionDoes the device have a user mappable memory range?

Important for the efficiency of the interface in cases where the data points are not arranged in a contiguous fashion.

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Integration Definition – Foreign Device DefinitionDoes the device have redundant communications capability?

This question is important to determine which software package is correct for your application.

I/A Series Integrator InformationThe DI30 has two ports. Each can talk to a separate device or as a redundant port.The MG30 has two ports. The second can be configured as a “B” bus to the same device.The FBM224 has four ports and a redundant port can be configured.

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Integration Definition – Foreign Device DefinitionHow many devices will be on this serial bus?

This question is important to decide upon the bus architecture.If only one device is on the bus, RS232, RS422, and RS485 are all valid choices.For multiple devices on the same bus, only RS485 supports multidrop.

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Integration Definition – Foreign Device DefinitionHow far away from the integrator will the device be?

This question is important to ask to determine which protocol/and or converters will be required.

For instance, if the distance is greater than 50 feet, then RS232 is not a good option without the use of converters.

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Design considerationsIn today's terms, serial communications have a very low throughput.

Example: Assume that a typical query takes 200 ms to reach the field device, the field device takes 100 ms to process the query and build the response message, then 200 seconds for the response to reach the integrator.

That equal 500 ms turnaround per query. In essence 2 queries per second.

This is why it is extremely important to gauge the total number of queries on a serial bus and use a conservative estimate for turnaround time.

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Design considerationsHow many queries will I have?

Each Modbus device on a bus will take a minimum of one query

Each different function code (including heartbeat) requires its own query.

If memory locations are not contiguous, and a “reserved” or “restricted” memory address is between the desired data points, then more than one query will be required per query range.

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Example1: I have a device from which I wish to obtain 10 discrete data points, 10 analog values, write 10 analog values, and write 10 discrete data points. This device supports heartbeat.

This interface would have five (5) queries and the update time should be set to no faster than 2.5 seconds.*

*actual turnaround times can be checked with a communications probe.

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Example2: I have 2 devices on the same RS485 bus from which I wish to obtain 10 discrete data points, 10 analog values, write 10 analog values, and write 10 discrete data points each. These devices support heartbeat.

This interface would have five (10) queries and the update time should be set to no faster than 5 seconds.*

*actual turnaround times can be checked with a communications probe.

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Integration Design Should you use a MG30, DI30, or a FBM224 for your implementation?

An MG30 is for Modbus RTU Master protocol only, but is very easy to configure.

A DI30 Can be Master or Slave, RTU or ASCII, and has settable parameters for communication timing adjustments, but is much more complex to configure.

An FBM224 is easy to configure, but is also for Modbus RTU Master protocol only and is only currently available for 6.5 and 7.1 versions.

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Integration Design

In Summary,

Use an FBM224 if you are at V6.5 or 7.1 and the device is a Modbus Slave.

Use a MG30 if at any other version and the device is a Modbus RTU Slave.

Use a DI30 if neither of the above apply.

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MG30/AB30/DI30 form factorMG30/AB30/DI30 form factor

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FBM224 form factorFBM224 form factor

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Device Integrator 30 Device Integrator 30 ConfigurationsConfigurations

Non Redundant Device Integrator

Redundant Device Integrator

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MG30 INTEGRATIONMG30 INTEGRATION

Non Redundant Configuration

Redundant Configuration

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DI 30 Integration InputsDI 30 Integration Inputs

FDRIN

FDIIN

FDBIN

ECBMessage

FDIDMS

Other

Blocks

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DI 30 Integration OutputsDI 30 Integration Outputs

FDROUT

FDIOUT

FDBOUT

ECBMessage

FDMSBL

Other

Blocks

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DI 30 Integration Master vs DI 30 Integration Master vs SlaveSlave

ECBMessage

FDSCAN

Data

Message

Master Configuration

Data Scanned at regular frequency

Set by FDSCAN Block Period

ECB FDIDMS

Data

Message

Slave Configuration

Data Identified and used

as it is sent from the

Field Device

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MODBUS INTEGRATOR MODBUS INTEGRATOR BLOCKSBLOCKS

AIN ALMPRI AOUT CALC CHARC CIN COUT DEP EXC GDEV IND

MAIN MCIN MCOUT MON MOVLV MTR PATALM REALM TIMR VLV

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ModBus 30 IntegrationModBus 30 Integration

ECBMDSCAN

BLOCK

AIN

CIN

AOUT

COUT

OTHER

BLOCKS

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Integration Design

Create a drawing showing the architecture of the interface consisting of the following elements:IntegratorCable and FTA for the IntegratorAny converters required for the interface.Identify the type of media for each cable (fiber-optic, Twin-axial, etc…)The dip-switch settings for the FTA based on the Definition information and the settings shown in each of the Integrator specific user documentation.

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Useful Tools for Modbus Implementation

Break-Out Box - This device connects in line with an RS232 bus to show signal voltage for all of the data and control lines for this protocol.

Communication (data) probe – This device also connects in line with the RS232 bus to show actual bytes of data as well as showing signal voltage for all the data and control lines.

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Modbus/Modsim simulation program - This application allows you to use a laptop (or tabletop) PC to emulate a Modbus Master or Modbus Slave device respectively, and view the modbus data bytes.

Null Modem Connectors – This device connects in line with the RS232 bus to correct one of the most common RS232 problems. It converts the control and data lines from a DTE to a DCE type.

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Assorted cables and connectors - Make sure that an assortment of cable types (9-pin versus 25-pin) and male-to-male and female-to-female adapters are available. Nothing stops implementation faster than not being able to physically attach a cable. If the implementation will use a RS485 bus, it is a good idea to have an extra RS232/RS485 converter available to use the RS232 only tools!

Modbus Device Vendor – Many times an implementation comes to a screeching halt because no one is available that can look inside the foreign device to verify basic communications settings. So if no one is available that knows the device well, then it is best to have a vendor representative present during implementation

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Steps to implement the interface

1. Verify Foreign device is ready for communication by using Modsim or similar modbus master emulator to query a specific modbus data point.

Once you can connect with this program, you can consider the foreign device ready for connection with the integrator.

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2. Connect the interface based on the Design information.

Be sure all dip-switch settings on the Integrator FTA are correct.

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3. Build the ECBs and one integrator specific block based on the individual integrator User Documentation.

Remember to put the appropriate ECBs on-line in System Management and to turn on the Compound for the selected data point. Note that DI30s can require multiple compounds for one data point.

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4. If the data point responds as desired, build any remaining ECBs and integrator specific block based on the individual integrator User Documentation.

Remember to put the appropriate ECBs on-line in System Management and to turn on the Compound for the selected data point. Note that DI30s can require multiple compounds for one data point.

If the point does not respond as desired, troubleshoot using the tools shown in the previous section.

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5. Connect the Integrator specific data block to the standard I/A Series blocks (such as AIN, CIN) for scaling and display.

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Example ECB Configuration

The type and quantity of ECBs to be configured depends upon which hardware/software is used (i.e. DI30, MG30, FBM224)

This example will use the MG30 configuration.

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Example ECB Configuration

The MG30 gateway requires the configuration of two ECBs

1. ECBPG – represents gateway and sets communication parameters2. ECB16 – represents the Modbus Device and contains specific information for that device.

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Example ECBPG Configuration


This parameter defines the number of active ports:1 = 1 Port 2 = 2 Ports

This parameter defines the Bus switching options1 = Bus A only 2 = Bus B only

3 = Bus A with bus B switching enabled4 = Bus B with bus A switching enabled

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Example ECB16 Configuration


Typically, 2 will work for any device.Specific device parameters are:

1 = AEG 484 2 = AEG 5843 = AEG 884 4 = AEG 984

0 = No Heartbeat 1 = Heartbeat

Do not enable heartbeat unless you are sure yourModbus device supports heartbeat.

This parameter defines the unique network addressof the Modbus Device.

Don’t confuse it with the memory addresses.

The valid range is 1 - 247

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ALLEN BRADLEY INTEGRATIONALLEN BRADLEY INTEGRATION

PLC PLC PLC PLC

KF OR KE

Module

AB 30

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AB 30 IntegrationAB 30 Integration

ECBABSCAN

BLOCK

AIN

CIN

AOUT

COUT

OTHER

BLOCKS

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AB INTEGRATOR BLOCKSAB INTEGRATOR BLOCKS

AIN ALMPRI AOUT CALC CHARC CIN COUT DEP EXC GDEV IND

MAIN MCIN MCOUT MON MOVLV MTR PATALM REALM TIMR VLV

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Application Workstation provides integration to third party devices

Multiple Media RS232 or RS485 Ethernet

Multiple Protocols Modbus AB Data Highway I/O Gate - DDE

Scaleable ValueBlocks

Other Integration ProductsOther Integration Products

AW50/70Integrator(w/ Foxblocks)

FieldbusModule

I/A Series Fieldbus

E-netAB PLC orGE PLC orSCADA SystemDDE I/O GateRS-232 or

RS485762 ControllersSCADA SystemModbusAB Data highway +DDE I/O Gate

Nodebus

1 a practical guide to device integration with an emphasis on the modbus serial protocol device...

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