GW Instek PFR Series Guide

Modbus RTU/TCP

PFR Series

START GUIDE

ISO-9001 CERTIFIED MANUFACTURER

This manual contains proprietary information, which is protected by

photocopied, reproduced or translated to another language without

prior written consent of Good Will company.

The information in this manual was correct at the time of printing.

However, Good Will continues to improve products and reserves the

rights to change specification, equipment, and maintenance

procedures at any time without notice.

Good Will Instrument Co., Ltd.

No. 7-1, Jhongsing Rd., Tucheng Dist., New Taipei City 236, Taiwan.

TABLE OF CONTENTS

Table of Contents

Overview ................................................................... 4

Quick guide function setting ..................................... 5

Modbus RTU .............................................................. 6

Introduction........................................................................................ 6

Using Modbus RTU .......................................................................... 8

Multiple Unit Connection ..............................................................10

Function check .................................................................................12

Modbus TCP ............................................................. 14

Introduction......................................................................................14

Using Modbus TCP.........................................................................16

Function check .................................................................................17

Data Type................................................................. 19

Char ....................................................................................................19

Uint16 ................................................................................................20

Uint32 ................................................................................................22

Float....................................................................................................23

Exception Code List .................................................. 25

Modbus RTU/TCP START GUIDE

Overview

This document serves as a comprehensive guide to the Modbus

functions. It begins with a “Quick Guide Function Setting”chapter,

offering users a straightforward method for rapid configuration.

The “Modbus RTU”chapter introduces the function codes, packet

formats, and setting steps of RTU, and provides practical examples.

Similarly, the chapter “Modbus TCP”explains that TCP has the

same function code as RTU, but its packet format is different. The

first address of the packet format is replaced by MBAP, and there is

no trailing CRC. This section also includes setup guidelines and

illustrative examples.

The “Data Type”section lists various data types used in Modbus,

accompanied by examples demonstrating their application.

Finally, the “Exception Code List”chapter is dedicated to outlining

the response codes for handling unexpected situations in Modbus

operations.

Note

This function is a non-standard function, and the

applicable firmware version must be higher than V1.33

(please refer to the user manual to check the firmware

version), and it needs to be activated or a license

purchased before the machine leaves the factory.

For more information, please contact your local dealer

or GW Instek at

www.gwinstek.com/marketing@goodwill.com.tw.

Quick guide function setting

RTU

TCP

1. Connect PFR IN port to a PC

using RS485/RS232 cable

with DB9 & RJ-45.

2. Set the F-29 (Interface Select)

setting to 1 (RS232) or 2

(RS485).

3. Set UART Baud Rate (F-71).

4. Set the F-72 (UART Data Bits)

setting to 1 (8 bits).

5. Set UART Parity (F-73).

6. Set UART Stop Bit (F-74).

7. Set the F-75 (UART TCP)

setting to 2 (Modbus RTU).

8. Set UART Address

(Modbus Slave Address) (F-

76).

9. Set the F-77 (UART Multi-

Drop control) setting to 0

(Disable).

1. Connect an Ethernet cable

from the network to the rear

panel Ethernet port.

2. Set the F-29 (Interface Select)

setting to 8 (Modbus TCP).

3. Set IP address (F-39~F-42).

4. Set Subnet Mask (F-43~F-46).

5. Set Gateway (F-47~F-50).

NOTE:

Socket server port number is

502 for Modbus master

application.

Modbus RTU/TCP START GUIDE

Modbus RTU

Introduction

Overview

Modbus RTU message consists of Address and

PDU, ending with CRC.

Modbus data is transmitted in frames, and each

frame has a determined starting point and ending

point.

In RTU mode, a minimum 3.5-character pause is

required at the beginning of the message. After the

last character is sent, there will be a 3.5-character

pause before a new message can be sent.

Frame2

>= 3.5 char

…

>= 3.5 char

Frame1

Function code

The function codes provided for use are as

follows.

Function code

Description

0x03

Read Holding Registers

0x06

Write Single Registers

0x10

Write Multiple Registers

Read Holding

Registers

(FC 0x03)

Request:

Address

Function

code

Starting

registers

Number of

CRC

Byte0

Byte1

Byte2,3

Byte4,5

Byte6,7

Response:

Address

Function

code

Byte count

Data

CRC

Byte0

Byte1

Byte2

Byte3~252

Last1,2

Modbus RTU

Write Single

Registers

(FC 0x06)

Request:

Address

Function

code

Starting

registers

Data

CRC

Byte0

Byte1

Byte2,3

Byte4,5

Byte6,7

Response:

Address

Function

code

Starting

registers

Data

CRC

Byte0

Byte1

Byte2,3

Byte4,5

Byte6,7

Write Multiple

Registers

(FC 0x10)

Request:

Address

Function

code

Starting

registers

Number

count

Data

byte

CRC

Byte0

Byte1

Byte2,3

Byte4,5

Byte6

Byte7~

253

Last1,2

Response:

Address

Function

code

Starting

registers

Data

CRC

Byte0

Byte1

Byte2,3

Byte4,5

Byte6,7

Modbus RTU/TCP START GUIDE

Using Modbus RTU

Overview

The PFR power supply can use Modbus RTU

protocol via RS232 and RS485. RS232 and RS485

are using PSU-232 and PSU-485 to connect PC.

The pin outs for the adapters are shown below.

PSU-232 RS232

cable with DB9

connector

DB-9 Connector

Remote IN Port(RJ-45)

Remark

Pin No.

Name

Pin No.

Name

Housing

Shield

Housing

Shield

Twisted

pair

5 1

9 6

1 8

(RJ-45)

(DB-9)

PSU-485 RS485

cable with DB9

connector

DB-9 Connector

Remote IN Port(RJ-45)

Remark

Pin No.

Name

Pin No.

Name

Housing

Shield

Housing

Shield

TXD-

RXD-

Twisted

pair

TXD+

RXD+

RXD-

TXD-

Twisted

pair

RXD+

TXD+

5 1

9 6

1 8

(RJ-45)

(DB-9)

Modbus RTU

Diagram of End

terminal

connector

End terminal

connector from

PSU-232 or PSU-

485 connection

kit.

End terminal connector

8 Pin Connector

Pin No.

Remarks

Internal shorted

Operation

1. Connect the RS232 serial cable

(include in the PSU-232

connection kit) or RS485 serial

cable (include in the PSU-485

connection kit) to the Remote IN

port on the real panel.

Connect the other end of the cable

to the PC.

RS 485 / 232 1

2. Connect the end terminal

connector (include in the PSU-232

or RS-485 connection kit) to the

Remote OUT port on the rear

panel.

RS 485 / 232

3. Press the Function key to enter the Normal

configuration settings.

Table

UART Menu

Function

Item

F-29

Interface

Select

0 = Disable, 1 = RS232, 2 = RS485,

3 = USB-CDC / NO Mass Storage,

4 = GPIB, 5 = LAN SOCKET,

6 = LAN WEB 7 = USB-TMC,

8 = Modbus TCP

F-71

UART Baud

Rate

0 = 1200, 1 = 2400, 2 = 4800,

3 = 9600, 4 = 19200, 5 = 38400,

6 = 57600, 7 = 115200

Modbus RTU/TCP START GUIDE

F-72

UART Data

Bits

0 = 7 bits, 1 = 8 bits

F-73

UART Parity

0 = None, 1 = Odd, 2 = Even

F-75

UART TCP

0 = SCPI, 1 = TDK (emulation

mode) 2 = Modbus RTU

F-76

UART Address

(Modbus Slave

Address)

01 ~ 30

F-77

UART Multi-

Drop control

0 = Disable, 1 = Master,

2 = Slave, 3 = Display information

Multiple Unit Connection

Operation

1. Connect the first unit’s IN port to a PC via

RS232 or RS485 serial cable.

Use the serial cables supplied in the PSU-232

or PSU-485 connection kit.

2. Plug in intermediate connector to the OUT port

on the first unit then using the slave serial link

cable (black plug) to connect intermediate

connector to the IN port of the second unit.

RS 485 / 232

OUT IN

Unit #1

RS 485 / 232

OUT IN

Unit #2

RS 485 / 232

OUT IN

Unit #N

End terminal

connector

To PC

RS232/RS485

serial cable

Slave serial

cable(black plug)

Slave serial

cable(black plug)

Intermediate

connector

3. Connect all the remaining units in the same

fashion until all the units have been daisy-

chained together.

4. Terminate the OUT port of the last unit with the

end terminal connector included in the PSU-

232 or PSU-485 connection kit.

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