FieldServer FS-8700-01 Modbus RTU, FS-8700-08 Modbus ASCII Instruction Manual

A Sierra Monitor Company

Driver Manual

(Supplement to the FieldServer Instruction Manual)

FS-8700-01 Modbus RTU

&

FS-8700-08 Modbus ASCII

There are several similarities between these two drivers and

we have incorporated them into the same manual to ensure

that our information stays current. Although both drivers

are referenced in this manual, they are different drivers and

need to be ordered separately."

APPLICABILITY & EFFECTIVITY

Effective for all systems manufactured after May 1, 2001

Instruction Manual Part Number: T28700-01

Rev. A.

Applicability and Effectivity

FS-8700-01_Modbus_RTU_(T28700-01) Driver Manual Table of Contents

Table of Contents

1. Modbus RTU/ Modbus ASCII Description ....................................................................... 3

2. Driver Scope of Supply..................................................................................................... 4

2.1. Supplied by FieldServer Technologies for this driver.................................................... 4

2.2. Provided by Supplier of 3rd Party Equipment................................................................ 4

3. Hardware Connections ..................................................................................................... 5

4. Configuring the FieldServer as a Modbus RTU or Modbus ASCII Client. ..................... 6

4.1. Data Arrays/Descriptors............................................................................................... 6

4.2. Client Side Connection Descriptors.............................................................................. 7

4.3. Client Side Node Descriptors ....................................................................................... 8

4.4. Client Side Map Descriptors......................................................................................... 9

4.4.1. FieldServer Related Map Descriptor Parameters.................................................. 9

4.4.2. Driver Related Map Descriptor Parameters........................................................... 9

4.4.3. Timing Parameters................................................................................................ 9

4.4.4. Map Descriptor Examples....................................................................................10

5. Configuring the FieldServer as a Modbus RTU or Modbus ASCII Server....................11

5.1. Server Side Connection Descriptors ...........................................................................11

5.2. Server Side Node Descriptors.....................................................................................12

5.3. Server Side Map Descriptors ......................................................................................13

5.3.1. FieldServer Specific Map Descriptor Parameters.................................................13

5.3.2. Driver Specific Map Descriptor Parameters .........................................................13

5.3.3. Map Descriptor Examples....................................................................................14

Appendix A. Advanced Topics – Modbus RTU..................................................................15

Appendix A.1. Data Types ..................................................................................................15

Appendix A.2. Single Writes................................................................................................16

Appendix A.3. Read/write Operation ...................................................................................16

Appendix A.4. Managing Floating points with Modbus ........................................................17

Appendix A.5. Connection to York Modbus Microgateway ..................................................18

Appendix A.6. Node_Offline_Response..............................................................................19

Appendix B. Modbus ASCII - Examples of FieldServer setup for typical clients ............20

Appendix B.1. FieldServer with GE Cimplicity as client .......................................................20

Appendix B.2. FieldServer with Intellution FIX as a client....................................................20

FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web:www.FieldServer.com

Tel: [phone] Fax: [phone] Toll_Free: 888-509-1970 email: [e-mail]

FS-8700-01_Modbus_RTU_(T28700-01) Driver Manual Page 3 of 21

1. Modbus RTU/ Modbus ASCII Description

The Modbus RTU and Modbus ASCII drivers allow the FieldServer to transfer data to and from
devices over either RS-232 or RS-485 using Modbus RTU or Modbus ASCII protocol
respectively. The driver was developed for Modbus Application Protocol Specification V1.1a"
from Modbus-IDA. The specification can be found at www.modbus.org. The FieldServer can
emulate either a Server or Client.

The information that follows describes how to expand upon the factory defaults provided in the
configuration files included with the FieldServer.

There are various register mapping models being followed by various vendors
To cover all these models FieldServer uses the following three Models

• Modicon_5digit – Use this format where addresses are defined in 0xxxx, 1xxxx, 3xxxx or
4xxxx format. A maximum of 9999 registers can be mapped of each type. This is
FieldServer driver’s default format.

• ADU –Application Data Unit address. Use this format where addresses of each type are
defined in the range 1-65536

• PDU –Protocol Data unit address. Use this format where addresses of each type are
defined in the range 0-65535.

The key difference between ADU and PDU is for example if Address_Type is ADU and address
is 1, the driver will poll for register 0. If Address_Type is PDU, the driver will poll for address 1.

Note 1: If vendor document shows addresses in extended Modicon (i.e. 6 digit) format like
4xxxxx then consider these addresses as xxxxx (omit the first digit) and use either ADU or PDU

Note 2: The purpose of providing 3 different ways of addressing the Modbus registers is to allow
the user to choose the addressing system most compatible with the address list being used. At
the protocol level, the same protocol specification is used for all three with the exception of the
limited address range for Modicon_5digit.

FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web:www.FieldServer.com

Tel: [phone] Fax: [phone] Toll_Free: 888-509-1970 email: [e-mail]

FS-8700-01_Modbus_RTU_(T28700-01) Driver Manual Page 4 of 21

2. Driver Scope of Supply

2.1. Supplied by FieldServer Technologies for this driver

FIELDSERVER TECHNOLOGIES PART # DESCRIPTION

FS-8915-10 UTP cable (7 foot) for RS-232 use
FS-8917-02 RJ45 to DB9F connector adapter
FS-8917-01 RJ45 to DB25M connection adapter
FS-8917-21 RS-485 connection adapter
FS-8700-01 (T28700-01) Driver Manual

2.2. Provided by Supplier of 3rd Party Equipment

PART # DESCRIPTION

Modbus RTU or Modbus ASCII device

FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web:www.FieldServer.com

Tel: [phone] Fax: [phone] Toll_Free: 888-509-1970 email: [e-mail]

FS-8700-01_Modbus_RTU_(T28700-01) Driver Manual Page 5 of 21

3. Hardware Connections

It is possible to connect a Modbus RTU or Modbus ASCII device to any of the existing serial
ports on the FieldServer1. These ports simply need to be configured for the appropriate driver in
the configuration file.

Configure the Modbus RTU or Modbus ASCII device according to manufacturer’s instructions.

1

Not all ports shown are necessarily supported by the hardware. Consult the appropriate Instruction

manual for details of the ports available on specific hardware.

FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web:www.FieldServer.com

Tel: [phone] Fax: [phone] Toll_Free: 888-509-1970 email: [e-mail]

FS-8700-01_Modbus_RTU_(T28700-01) Driver Manual Page 6 of 21

4. Configuring the FieldServer as a Modbus RTU or Modbus ASCII Client.

For a detailed discussion on FieldServer configuration, please refer to the FieldServer
Configuration Manual. The information that follows describes how to expand upon the factory
defaults provided in the configuration files included with the FieldServer (See “.csv” sample files
provided with the FieldServer).

This section documents and describes the parameters necessary for configuring the FieldServer
to communicate with a Modbus RTU or Modbus ASCII Server.

4.1. Data Arrays/Descriptors

The configuration file tells the FieldServer about its interfaces, and the routing of data
required. In order to enable the FieldServer for Modbus RTU or Modbus ASCII
communications, the driver independent FieldServer buffers need to be declared in the
“Data Arrays” section, the destination device addresses need to be declared in the “Client
Side Nodes” section, and the data required from the Servers needs to be mapped in the
“Client Side Map Descriptors” section. Details on how to do this can be found below.

Note that in the tables, * indicates an optional parameter, with the bold legal value being the
default.

Section Title

Data_Arrays

Column Title Function Legal Values

Data_Array_Name Provide name for Data Array

Provide data format. Each

Data_Array_Format

Data Array can only take on
one format.
Number of Data Objects. Must
be larger than the data

Data_Array_Length

storage area required by the
map descriptors for the data
being placed in this array.

Example

// Data Arrays
Data_Arrays
Data_Array_Name, Data_Array_Format, Data_Array_Length
DA_AI_01, UInt16, 200
DA_AO_01, UInt16, 200
DA_DI_01, Bit, 200
DA_DO_01, Bit, 200

Up to 15 alphanumeric
characters
FLOAT, BIT, UInt16, SInt16,
Packed_Bit, Byte,
Packed_Byte, Swapped_Byte

1-10,000

FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web:www.FieldServer.com

Tel: [phone] Fax: [phone] Toll_Free: 888-509-1970 email: [e-mail]

FS-8700-01_Modbus_RTU_(T28700-01) Driver Manual Page 7 of 21

4.2. Client Side Connection Descriptors

Section Title

Connections

Column Title Function Legal Values

Port

Baud* Specify baud rate

Parity* Specify parity
Data_Bits*

Stop_Bits*

Protocol

Handshaking* Handshaking is not supported
Poll Delay*

Example

Change protocol to MB_ASCII to use Modbus ASCII protocol

// Client Side Connections

Connections
Port, Baud, Parity, Data_Bits, Stop_Bits, Protocol, Handshaking, Poll_Delay
P8, 9600, None, 8, 1, Modbus _RTU, None, 0.100s

Specify which port the device is
connected to the FieldServer

Specify data bits
Specify stop bits

Specify protocol used

Time between internal polls

P1-P8, R1-R22

110 – 115200, standard baud
rates only. 9600
Even, Odd, None

7, 8
1 (Vendor limitation)

Modbus RTU
Modbus _RTU
Modbus ASCII
MB_ASCII

None

0-32000s, 0.05s

2

Not all ports shown are necessarily supported by the hardware. Consult the appropriate Instruction

manual for details of the ports available on specific hardware.

FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web:www.FieldServer.com

Tel: [phone] Fax: [phone] Toll_Free: 888-509-1970 email: [e-mail]