FS-8700-32 – Modbus Tek-Air

FieldServer Driver


Modbus Tek-Air


The Tek-Air Modbus RTU driver allows the FieldServer to transfer data to and from Tek-Air devices over either RS-232 or RS-485 using the Enhanced Tek-Air Modbus RTU protocol. Modbus_Tekair is the same as Modbus_RTU, except that it has the ability to concentrate the bytes of data in the packet to create floating point values. The order in which the bytes are combined and the address range used was developed specifically for the Tek-Air/Modbus interface. To accommodate this, the driver must be configured to poll using odd numbered addresses as two integer registers are used for every floating point value. If this value is stored in a floating point data array, it will be retrievable in the correct format on the Server side. Note that the Tekair “Double” data type is not supported.


Fieldserver Mode Nodes Comments
Client 1 Only 1 client node allowed on Multidrop systems
Server 254 Actual electrical loading may reduce number of usable server nodes


Formal Driver Type


Client or Server


Connection Information

Connection type: RS-232 or RS-485 (Two wire, Half-Duplex)
Baud Rates: 300; 600; 1200; 2400; 4800; 9600; 19200; 28800; 38400 Baud
Data Bits: 7,8
Stop Bits: 1,2
Parity: Odd, Even, None
Multidrop Capability Yes


Devices tested

Device Tested (FACTORY, SITE)
SmartLab Controller Site

Connection configurations


Connection Notes

The actual amount of stations on a network may be limited due to electrical loading limitations.

Communications functions – Supported functions at a glance:

Data Types Supported

FieldServer Data Type Description (or Device Data Type)
Analog Input Analog Input Registers
Digital Input Discrete Input Registers
Analog Register Input and Output Registers
Digital Register Input and Output Registers
Analog Output Analog Output Registers
Digital Output Discrete Output Registers


Read and Write Operations supported

FieldServer as a Client FieldServer as a Server
Read Analog Status: Provide Analog Status:
Read Output Registers (4xxxx)Read Input Registers (3xxxx) Provide Output Registers (4xxxx)Provide Input Registers (3xxxx)
Read Binary Status: Provide Binary Status:
Read Discrete Output Status (0xxxx)Read Discrete Input Status (1xxxx) Provide Discrete Output Status (0xxxx)Provide Discrete Input Status (1xxxx)
Write Analog Setpoints: Accept Analog Setpoints:
Preset Single Register (4xxxx)Preset Multiple Registers (4xxxx) Accept Preset Single Register (4xxxx)Accept Preset Multiple Registers (4xxxx)
Write Binary Commands: Accept Binary Commands:
Force Single Coil (0xxxx)Force Multiple Coils (0xxxx) Accept Force Single Coil (0xxxx)Accept Force Multiple Coils (0xxxx)


Unsupported Functions and Data Types

Function Reason
Programming messages FieldServer is a data transfer device, and as such, programming messages are not required


Unsupported Devices or Protocol Options

Device Details



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