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
copyright. All rights are reserved. No part of this manual may be
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
3
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
Register List ............................................................. 27

Modbus RTU/TCP START GUIDE
4
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/[e-mail].

Quick guide function setting
5
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
6
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
register
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
7
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
8
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
2
RX
7
TX
Twisted
pair
3
TX
8
RX
5
SG
1
SG
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
9
TXD-
6
RXD-
Twisted
pair
8
TXD+
3
RXD+
1
SG
1
SG
5
RXD-
5
TXD-
Twisted
pair
4
RXD+
4
TXD+
5 1
9 6
1 8
(RJ-45)
(DB-9)

Modbus RTU
9
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
3
Internal shorted
7
4
Internal shorted
8
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
2
3. Press the Function key to enter the Normal
configuration settings.
Table
UART Menu
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
10
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.