Varec 4000 manual Modbus Support over Mark/Space Host Interface

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4000	Theory of Operation

7.11Modbus Support over Mark/Space Host Interface

The ATT permits Modbus communications over the Mark/Space data highway. The Modbus request message is placed into a Mark/Space message frame. The ATT processes the request message and places the Modbus reply in a Mark/ Space reply frame.

This option is only available with systems using the Model 6840 Tank Polling Unit.

7.12Compatibility with Varec Tank Polling Unit

The Mark/Space communications provided by the ATT are compatible with the Varec Tank Polling Unit (TPU). This permits the ATT to be multi-dropped on the same Mark/Space data highway as the Varec 1800, Varec 1900, and MFT/ HIU devices.

If the EIA485 communications interface is installed in the ATT, it can be multi-dropped on an EIA485 data highway, RTU 8130 along with any Modbus compatible device, including the Model 6850 Field Interface Converter.

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Contents Installation Operations Manual Page Copyright Disclaimer of Warranties Safety Precaution Definitions Safety Precautions Tank Gauge Transmitter Introduction Tank Gauge Transmitter Glossary Tank Gauge Transmitter Viii Introduction Using This ManualConfiguration OperationConstruction Installation Part Number Gauge Adapter Kit Mounting the EquipmentConnecting Input Power WiringATT Wiring Wiring PreparationTerminal Block One TB1 Terminal Block Two TB2 Connecting Host CommunicationTypical EIA485 Wiring ATT EIA485 WiringTypical EIA485 System Wiring Typical Mark/Space Field Wiring ATT Mark/Space WiringInstallation Checkout Connecting the RTDConnecting the Handheld Terminal Wiring CompletionFunction Key Description ConfigurationConfiguration Parameters 1200 Hand Held TerminalTerminal Mode Configuration 1200 Hand Held Terminal Terminal Mode OperationMenu Operation Main Menu Description Main MenuSummary Menu Description Summary MenuConfiguration Menu Description Configuration MenuHost Menu Description Host MenuQuick Setup Imperial Fractional 1900 Quick Setup Defaults General ConfigurationHost Configuration Imperial Decimal 1900 Quick Setup Defaults 3 0-20 Meter 1900 Quick Setup Defaults 4 0-30 Meter 1900 Quick Setup Defaults 8 0-30 Meters 1800 Series Transmitter Quick Setup Imperial Fractional 1800 Series Transmitter Quick SetupImperial Decimal 1800 Series Transmitter Quick Setup 7 0-20 Meters 1800 Series Transmitter Quick SetupImperial Modbus Quick Setup Defaults Metric Modbus Quick Setup Defaults Maintenance and Troubleshooting MaintenanceBattery Replacement Troubleshooting ATT Error Status ConditionsError Message Description ATT Configuration Error Checking ATT Status ConditionsStatus Condition Description Host Communication Loopback Tests Model 1200 Error MessagesEnvironmental SpecificationsSpecifications and Physical Characteristics Input PowerLevel Measurement Agency Acronym Requirement Safety Agency ApprovalsIntrinsic Safety Explosion ProofMajor System Assemblies and Components Assembly/Component Part NumberCommunications Order CodesOrder Codes CPU Board Theory of OperationHost Communications Interfaces Back-up BatteryStatus Inputs and Outputs Atti Communications PortEncoder Battery Backup Temperature MeasurementHost Communication Mark/Space Host Interface Function NumberNumber Exception Compatibility with Varec Tank Polling Unit Modbus Support over Mark/Space Host InterfaceTheory of Operation Model 4040 Display Unit ATT Family of ProductsDigital Inputs Relay SpecificationsModel 4050 Digital Input/Output Unit Digital OutputsModbus Implementation IntroductionImplementation Modbus Implementation Functions and Data Formats Integer RegistersTerm Definition Integer Data Host RequestATT Response Character Data Packed Bit Data Coded DataFloating Point Data Floating-Point RegistersFloating-Point Data Two 16-bit Registers FormatOne 32-bit Register Format Exception Response Reason Status BitsStatus Bit Data Exception ResponsesData Out of Range Loopback TestHardware Implementation Register Number Type Description Integer Register MapRegister Number Sw Ver0-1 Noise Reject Type Status Bit Register Map Floating Point Register MapModbus Implementation 10.3 4000LJFMO Optional Interfaces10.1 4000TIFMO 10.2 4000GEFMO10.6 4000GMFMO 10.5 4000WBFMOAdv Hi Level GlossaryDband TSU Tank Gauge Transmitter 4000 Your official representative Your offical representative