Modbus Slave Driver

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Introduction

Modbus is a communications protocol for PLC Devices openly published by Modicon (now part of Schneider Electric). Since its publication in 1979 Modbus has been widely adopted as a communications protocol for PLC Devices and other types of device.

The Modbus Slave driver receives and processes requests from Modbus drivers in other products. The Modbus slave driver supports these variants of the Modbus protocol:

ProtocolDescription
Modbus RTU8-bit serial binary protocol
Modbus ASCII7 bit serial ASCII protocol
Modbus TCPTCP/IP protocol

Supported Modbus Commands

The Modbus Slave Driver supports these Modbus commands:

CommandDescription
01Read coil status
02Read input status
03Read holding registers
04Read input registers
05Force single coil
06Preset single register
08Diagnostics
11Read comm event counter
15Force multiple coils
16Preset multiple registers
17Report Slave ID
22Mask Write Holding Register

The Diagnostics Command (08) supports these sub-function values:

Sub-FunctionDescription
0Echo data
1Restart communication
2Return diagnostic register
10Clear counters and diagnostic register
11Return bus message count
12Return bus communication error count (CRC)
13Return bus exception error count
14Return slave message count
15Return slave no response count
16Return slave NAK count
17Return slave busy count
18Return bus character overrun count

Fernhill SCADA Modbus Slave Tags

The Modbus Slave driver provides these tag types to support communication using the Modbus protocol:

IconTag TypeVersionDescription
Channel IconModbus Slave TCP Channel Tag3.10A TCP/IP Server allowing connections from Modbus drivers in other products.
Channel IconModbus Slave Serial Channel Tag3.10A serial port used to receive and process Modbus requests.
PLC Device IconModbus Slave Device3.10A virtual Modbus device.

Further Information

Modbus Protocol

For a description of the Modbus Protocol.

Fernhill SCADA Drivers

For information about other drivers available in Fernhill SCADA.

Glossary

For the meaning of terms used in Fernhill SCADA.