B&B Electronics MES1A, MES1B manual Slave Address / Unit ID Source, For Auto, …255

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Configuring the MES1A/B

Slave Address / Unit ID Source

All devices connected to a TCP/IP network require a unique IP address. Each MES1A/B Converter has a unique IP address on the network, allowing messages to be directed to it. However, when multiple Modbus/RTU devices are connected to the RS-485 bus of an MES1B there must be a way to address them individually.

Standard Modbus/RTU fields are encapsulated inside Modbus/TCP messages. Modbus/RTU’s Slave Address field is called the Unit ID in Modbus/TCP. The Unit ID is used to specify a particular Modbus/RTU device on the serial side of the MES1A/B. When the MES1A/B receives a message (sent to its IP address), it looks at the Unit ID field of the message and passes the message to the specified slave.

0 for Auto

Setting the Slave Address field to 0 allows the MES1A/B to use the Unit ID received from a Modbus master to direct messages to a specific slave address. The MES1A/B receives the Unit ID number on the Modbus/TCP side and passes it along as the Slave Address on the serial side of the converter.

1…255

Unfortunately, some early Modbus/TCP products assumed that each IP address would have only one slave. These products always set their Unit ID to 0 (relying on the IP address only to address the slave). The lack of an appropriate Unit ID presents a problem for the MES1B. It must include a Slave Address in its messages to Modbus/RTU slaves.

To overcome this problem, the MES1A/B Slave Address field can be set to the address of one Modbus/RTU slave (any number in the range of 1 to 255). This limits the number of slaves that can be connected to the MES1A/B to one, but ensures that when any message for the MES1A/B’s IP address is received (regardless of its Unit ID), it is passed along to the slave.

To configure the Slave Address field:

•If Modbus TCP masters on your system use appropriate Unit ID addresses, select 0. You will be able to connect multiple Modbus/RTU slaves with RS-485 interfaces to an MES1B.

Manual Documentation Number: MES1A/MES1B-2106m

PN7138-rev001

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 – www.bb-elec.com

B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445 – www.bb-europe.com

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Contents Models MES1A, MES1B Modbus TCP Modbus Ascii / RTU ConvertersManual Documentation Number MES1A/MES1B-2106m International Headquarters Page Manual Documentation Number MES1A/MES1B-2106m PN7138-rev001 Page Table of Contents Configuring the MES1A/B Modbus Basics Manual Documentation Number MES1A/MES1B-2106m Introduction About this ManualSupport About Your MES1A/B Converter Features Hardware Overview Package ChecklistIndicators, Switches and Connectors Power LEDReset Switch Link LEDActivity LED RS-422/485 Connector MES1B only RS-422/485 Switch MES1B onlyEthernet Port Connector DB-9M Serial Port Connector MES1A onlyRS-485 Two-Wire Mode RS-422/485 Four-Wire ModePower Connector Connecting the HardwareMES1A Connections MES1B Connections Hardware Overview QuickStart Getting StartedDiscover the MES1A/B on the Network Using the Device Installer Software Installing the Device InstallerSystem Requirements Discovering Devices Starting the Device InstallerGetting Device Details Device Installer Main WindowPress Enter to go into Setup Mode Connecting to the MES1A/BTelnet Configuration Tab with Settings Getting Started Telnet Configuration Tab Configuring the MES1A/BUnit ID to IP Address Table Navigating the Configuration MenuTo Reconfigure the MES1B, to Factory Settings Saving Configuration SettingsReconfiguring to Factory Settings To Reconfigure the MES1A to Factory SettingsIP Address Network/IP SettingsDefault Gateway Auto-IPStatic IP Address Serial and Mode Settings Telnet Configuration PasswordNetmask Protocol Attached DeviceSerial Protocol Serial Interface MES1A Serial Interface MES1B Serial Interface Serial Parameters Modem/Configurable Pin SettingsAdvanced Modbus Protocol Settings Menu Advanced Modbus Protocol SettingsSlave Address / Unit ID Source For Auto…255 = Yes Allow Modbus BroadcastsUse MB/TCP 00BH/00AH Exception Responses = NoDisable Modbus/TCP Pipeline Character TimeoutMessage Timeout Close Idle TCP Sockets After Unit ID to IP Address Lookup Table SettingsSerial TX Delay after RX Swap 4x/0H to Get 3x/1xRedundant Entry Retries After Add, Delete, Exit Select FunctionModbus Address From/To Slave IP Address Using Other Device Installer Features Managing Device ListsCreating a New Device List Device List Display Options Display Devices Using IconsSaving Device Lists Opening Device ListsAdding a Device Manually Display the Hardware MAC AddressDisplay the Device Name Using Device Installer to Assign an IP Address Assigning an IP Address using Device InstallerUsing the Devices Details Tab Adding Info to the Device Details Tab Upgrading FirmwareSaving Setup Records Installing Pre-Saved Configuration FilesSave Setup Records Dialog Box Installing Setup RecordsLogging Search and Upgrade Data Options Window, Customization Tab Using Help Using PingUsing Other Device Installer Features Modbus ASCII/RTU Modbus BasicsModbus/TCP Hints and Tips Modbus Basics Swap 4x/0H to get 3x/1x Appendix a Default Configuration SettingsDefault Configuration Settings Manual CD-ROM disc Appendix B Product SpecificationsProduct Specifications Dimensional Diagram of the MES1A Appendix C Dimensional DiagramsDimensional Diagram of the MES1B DTE Appendix D Serial ConnectionsMES1B Terminal Block Pin-out for RS-485 Two-Wire Operation Appendix E Network Connections RJ-45 Pin Signal Wire ColorNetwork Connections Declaration of Conformity