PS-7-M Communication Specifications Guide

Keep this guide for easy reference.
Carefully read this guide prior to use or maintenance for safe
operation.

Instruction Manual No.
GAE-159-01
April 2024

Revision History
Revision00
01Document No.
GAE-159-00
GAE-159-01

Date
June 2020
April 2024

Contents of change
Initial issue.
6.5 Register Address MapiTable of Contents

Revision History........................................................................................................................................... i
1

Introduction ..........................................................................................................................................1
1.1 Related Publications ...................................................................................................................2
1.2 Overview .....................................................................................................................................3
1.3 Trademark Registration...............................................................................................................3
1.4 Remarks ......................................................................................................................................3
1.5 Symbols Used in this Instruction Manual ....................................................................................42

Precautions .........................................................................................................................................53

Unit Structure ......................................................................................................................................64

Communication Specifications ............................................................................................................7
4.1 Modbus RTU (RS-485) Communication Specifications ..............................................................8
4.2 Modbus TCP (Ethernet) Communication Specifications .............................................................85

Connection Specifications ...................................................................................................................9
5.1 System Configuration ............................................................................................................... 10
5.2 Wiring Procedure ..................................................................................................................... 125.2.1 Modbus RTU (RS-485) Wiring Procedure ..................................................................... 13
5.2.2 Modbus TCP (Ethernet) Wiring Procedure .................................................................... 15
5.3 Communication Setup .............................................................................................................. 17
5.3.1 DIP Switches .................................................................................................................. 17
5.3.2 Status LEDs ................................................................................................................... 22

6

Communication Protocol .................................................................................................................. 23
6.1 Modbus Communication Protocol Overview ............................................................................ 24
6.1.1 Message Configuration .................................................................................................. 24
6.1.2 CRC-16 Calculation (for Modbus RTU only) ................................................................. 26
6.1.3 Communication Procedure ............................................................................................ 26
6.1.4 Modbus RTU Communication Interval ........................................................................... 28
6.1.5 Differences between Modbus TCP and Modbus RTU Protocols ................................... 29
6.2 Function Codes ........................................................................................................................ 30
6.3 Response in the Event of an Error ........................................................................................... 31
6.3.1 Error Codes (Exception Codes) ..................................................................................... 32ii

6.4 Message Examples .................................................................................................................. 33
6.4.1 Function Code 03 (Read Single/Multiple Holding Registers) ........................................ 33
6.4.2 Function Code 06 (Write Single Holding Register) ........................................................ 35
6.4.3 Function Code 16 (Write Multiple Holding Registers) .................................................... 37
6.4.4 Function Code 23 (Read and Write Multiple Holding Registers) ................................... 39
6.4.5 Exception Response (Response in the event of an error)............................................. 41
6.5 Register Address Map .............................................................................................................. 42
7

Device Status Information ................................................................................................................ 49
7.1 Gas Alarm Operation ............................................................................................................... 50
7.2 Trouble Alarm Operation (Fault Alarm Operation) ................................................................... 51
7.3 Test Mode Setup and Operation .............................................................................................. 52
7.4 Maintenance Mode Setup and Operation ................................................................................ 53
7.5 Full Scale Codes ...................................................................................................................... 55

8

Troubleshooting ................................................................................................................................ 56

iii

1 Introduction
Thank you for purchasing the New Cosmos PS-7-M series extractive pump gas detector(hereinafter “detector” or “product”).
This detector consists of a main unit and a base unit. A main unit includes a display, a pump anda sensor, while a base unit has external communication terminals to connect to external devices.
This product supports RS-485 and Ethernet communications.

-1-1.1 Related Publications
The following documents have been prepared to guide your installation and use of this product.
1. PS-7-M series gas detector’s instruction manual (Doc.No.GAE-138-xx)
This manual provides the following information to ensure safe use of the product.
 Safety precautions
 Installation and wiring
 Basic configuration, block diagram, unit dimensions and components
 Operation and mode setting
 Maintenance, parts replacement, and action to take in the event of a failure
One manual is provided per system, not per unit.
2. PS-7 gas detector’s operation manual for administrators (Doc.No.GAE-019-xx)
This manual is intended for your system administrators/supervisors.
 Password
 Changing settings
All the items set for this product (e.g. alarm set values) are password-protected.
One manual is provided per system, not per unit.
3. PS-7 pyrolyzer’s operation manual (Doc.No.GAE-020-xx)
This manual describes installation and replacement procedure for a pyrolyzer (sold separately).
A manual is provided per system if the unit includes a sensor unit with pyrolyzer.
4. PS-7-M communication specifications guide (Doc.No.GAE-159-xx)
This guide provides the communication specifications and procedure to establish communication withexternal devices.
One guide is provided per system, not per unit.
5. PS-7-M IP address setting guideThis guide describes how to set/change the IP address by using a web browser to establish communication
with external devices.
One guide is provided per system, not per unit.

-2-

1.2 Overview
This product uses the Modbus RTU (RS-485) and Modbus TCP (Ethernet) communication protocols. This
guide describes the Modbus interface communication specifications for exterior communication of thisproduct.
This guide is intended for administrators/supervisors who perform device setups and data collection from the
Modbus master, by connecting the master and the PS-7-M series gas detectors (Modbus slaves) and using
the Modbus protocol function codes and their functions.
For the basic operation of the product, refer to the PS-7-M series gas detector’s instruction manual.
This guide describes the communication specifications and connection method for using the product’s
Modbus communication functions. For the operation and handling of the external Modbus devices that
send/receive data to/from this product, refer to each device’s instruction manual.

1.3 Trademark Registration
Modbus® is a registered trademark of Modicon Inc. (AEG Schneider Automation International S.A.S).
Their company name and product name are also their trademarks and are used in this guide with no TM or “®”symbol.

1.4 Remarks
Prior to use, carefully read this guide for correct use.
Unauthorized copying and replication of the contents of this guide, in whole or in part, are strictly prohibited.
The contents of this guide are subject to change without notice.
This guide has been prepared with the utmost care. If any incorrect description comes to your notice, pleasecontact us for correction.

-3-

1.5 Symbols Used in this Instruction Manual
Operators’ safety has been put first in designing this product. However, there exist someunavoidable risks due to the system characteristics. In this guide, safety symbols are divided into
three categories, Danger, Warning and Caution, depending on the severity and magnitude of therisks. Carefully read the contents related to the precautions before starting operation or
maintenance work.
This guide uses DANGER, WARNING, CAUTION and NOTE symbols to draw attention toprocedures, materials, methods and processes that require particular attention.

Indicates an imminently hazardous situation that can result in death or serious injury.

Indicates a potentially hazardous situation that may result in death or serious injury.

Indicates a hazardous situation that may result in minor injury or property damage.

NOTE

Provides supplemental or useful information on product handling.

-4-2 Precautions
Carefully read the following precautions for correct use.
Use this product in accordance with the applicable laws and regulations.
Wiring and installation should only be performed by a qualified electrician with knowledge of
wiring/installation procedures in accordance with the applicable technical standards.

 This product is not explosion-proof and should not be installed in a hazardous area.

 Ground the product to prevent electric shocks.
 In the event of a gas leak alarm, follow safety procedures in accordance with yourcompany's regulations.

 Do not disassemble, modify, or alter the structure of the product or its electrical circuits;
doing so may compromise product performance.

 This product is not drip-proof and should be kept away from splashing water or rain.

-5-3 Unit Structure
The PS-7-M gas detector consists of a main unit and a base unit.
For the details on the main and base units and other parts of the detector, refer to the PS-7-M seriesgas detector’s instruction manual.

Item

Component

Description/Function

1

Main unit

Includes a display, a pump and a sensor.

2

Base unit

Used for wiring and tubing.
Includes two terminal blocks for exterior communication.

-6-

4 Communication Specifications
This chapter describes the communication specifications for this product.
Single-master-multiple-slave (SMMS) communication method is used for a system configuration inwhich Modbus slaves (PS-7-M series gas detectors) can send/receive data to/from the Modbus
master.
It is assumed that the Modbus master (high-order device) is a personal computer, a programmable
logic controller (PLC), or a fieldbus controller in case of Modbus TCP.

-7-

4.1 Modbus RTU (RS-485) Communication Specifications
Modbus RTU (RS-485) communication specifications
Item
Specifications
Communication protocol
ModbusCommunication specifications
RS-485 interface
Communication method
Two-wire half-duplex asynchronous
System configuration
Single-Master-Multiple-Slave (SMMS)
Multi-drop
Data format
Modbus RTU mode (hexadecimal number (hex code))Start bit: 1 bit
Data length: 8 bits (fixed) (LSB first)
Stop bit: 1 bit (fixed)
Parity bit: No parity (fixed)
Communication speed
Fixed at 9600 bps
Physical layer protocol
ANSI/EIA/TIA RS-485
Number of connected devices
Up to 32 units including masterMaximum transmission distance
1.2km when the communication speed is 9600 bps
Terminal resistance
120 Ohm
Can be set to on/off with switch
Error checking method
CRC-16

4.2 Modbus TCP (Ethernet) Communication Specifications
Modbus TCP (Ethernet) communication specifications.
Item
Specifications
Communication protocol
Modbus (TCP/IP)
Communication specifications
EthernetCommunication interface
RJ-45 Ethernet IEEE 802.3af/ANSI X3.263
System configuration
Single-Master-Multiple-Slave (SMMS)
Port No.
No.502 (fixed: Modbus)
Communication speed
Max. 10 Mbps/100 Mbps
Physical layer protocol
100BASE-TX
Number of connected devices
Up to 254 units
Maximum transmission distance
100 m (distance up to the switching hub)Applicable cable
Unshielded Twisted Pair (UTP) cable(Category: 5e or higher)
IP address
192.168.100.1 (by default when shipped out)
Can be changed from the base unit or web browser.

-8-5 Connection Specifications
This chapter describes the connection specifications for this product.

-9-5.1 System Configuration
Typical communication system configurations are given below as examples.
(1) Typical Modbus RTU (RS-485) configuration
Wire multiple slaves in series (multi-drop wiring).

MasterG＋－120 terminal resistor
RS-485(＋)

RS -485(MODBUS RTU)

RS-485
( －)

G

＋

－

G

＋

－

G

＋

－

G

＋

－

120 terminal
resistor is on.

Unit ID: 1

Unit ID: 2

Unit ID: 3

Unit ID: N
N: 7 to 254

Slaves(The maximum number of connected slaves is 31)
Use a 120 Ohm terminal resistor at each end of the communication line.
There is a terminal resistor switch on the base unit. Set the switch to the ON position when theterminal resistors are used at both ends of the line (one resistor at each end).

- 10 -

(2) Typical Modbus TCP (Ethernet) configuration

MasterSlavesUnit ID: 1

PoE-HUB*1

Ethernet

Unit ID: 2(MODBUS TCP)
Fieldbus controller*2

Unit ID: 3

L2-Switch

Unit ID: 4

PoE-HUB*1Unit ID: 5

Unit ID: 6

Unit ID: N
N: 7 to 254

NOTE*1. If the switching hub is not PoE-compliant, provide 24 VDC to PS-7-M units.
*2. In case of using a fieldbus controller as a Modbus TCP master.

- 11 -

5.2 Wiring Procedure
This section explains how to establish a Modbus (RS-485 or Ethernet) network .
For detailed wiring procedure, refer to the PS-7-M series gas detector’s instruction manual.

Turn off the gas detector before wiring to prevent electric shocks.

 For precautions to be taken while wiring other than the Modbus terminals wiring, refer to 6.
“Installation and Wiring” of the PS-7-M series gas detector’s instruction manual.
 Before powering on the unit, ensure the wiring is correct by referring to 6-1. “Wiring
Procedure” of the PS-7-M series gas detector’s instruction manual and the delivery
specifications if any.
 The analog output line and power line of the gas detector are not isolated from each other.
When using with external devices, provide isolation to prevent noise from other power lines
from interfering with the analog output of the detector.
 When wiring, place wires to avoid potential noise sources (e.g. large power transformers,
motors, and powers supply units).
 Keep the connection cables (power and signal lines from the detector) away from otherpower lines.

 When wiring, place wires to avoid mechanical stress on the wiring.

- 12 -

5.2.1

Modbus RTU (RS-485) Wiring Procedure
Establish the Modbus RTU (RS-485) communication by taking the following steps.

When using the 24 VDC power supply, ensure that the power supply is 24 VDC 10%.

Applicable cables: Dia.8–11mm x 2pcs. Use appropriate cables for the installation environment.

Terminal resistor
終端抵抗
switchスイッチ

RS-485
RS-485 terminals

通信用端子

Grommetグロメット

1) Run a RS-485 digital signal cable thru the grommet (located at the bottom of the base unit), andconnect the cable wires to their corresponding RS-485 terminals.
Component
RS-485
terminals

Marking
on board
A
B
GND

Function
RS-485 (＋)
IN/OUT
RS-485 (－)
IN/OUT
Shielded- 13 -

Recommended cable
2-core shielded twisted pair cable2) Run a power cable thru the grommet (located at the bottom of the base unit), and connect thecable wires to their corresponding power terminals

Power terminals

Component
Power terminals(Thread size: M3)

Marking
on boardP
N

NOTE

Function
Polarity: ＋
Power input (24 VDC)
Polarity: －Power input (24 VDC)

Recommended cable
2-core CVV cable Single-point grounding (grounding at a single point) is mandatory. When thecable shield from the gas detector is grounded on the power supply side, DO
NOT ground the shielded cable to the Earth terminal located inside the gas
detector (on the terminal block for power cable) to avoid 2-point grounding.
 If used in a place exposed to electrical noises, use a shielded twisted pair (STP)
cable. When using STP cable, provide signal grounding so that all theconnected devices are ground-looped (ground continuity) to avoid noiseinterference due to ground discontinuity.
 Set the terminal resistor switch (located on the base unit) to the ON position
when terminal resistors are used at both ends of the circuit.

3) Perform the communication setup (select the “RS485” mode and set the unit ID with the DIP
switches (mode change switch and address setting switches). Refer to pages 19 and 20 for theprocedure).
4) Set the base unit power switch to the ON position.

- 14 -

5.2.2

Modbus TCP (Ethernet) Wiring Procedure
Establish the Modbus TCP (Ethernet) communication by taking the following steps.

 When using the 24 VDC power supply, ensure that the power is 24 VDC 10%.
 When using the PoE power supply, ensure that the LAN cable is securely connected.
Bottom view of base unit

GrommetRJ-4 jack1) Connect the LAN cable to the RJ-45 jack on the bottom of the base unit.
Component
RJ-45 jack

Function
8P8C
Ethernet and PoE＋Power Device port

Applicable cables
100BASE-TX unshielded twisted pair (UTP) cable
Category: 5e or greater
Cable length: Max.100 m (distance to HUB)

When using a PoE-compliant switching hub (PoE HUB)
Go to step 2).

Turn off the PoE before disconnecting the LAN cable from the RJ-45 jack.
When using a non-PoE-compliant switching hub (PoE HUB)
24 VDC power supply is required.
Run the power cable thru the grommet and connect the cable wires to their corresponding power
terminals (located on the base unit).

- 15 -

NOTE

 Single-point grounding (grounding at a single point) is mandatory. When thecable shield from the gas detector is grounded on the power supply side, DO
NOT ground the shielded cable to the Earth terminal located inside the gas
detector (on the terminal block for power cable) to avoid 2-point grounding.

 If used in a place exposed to electrical noises, use a shielded twisted pair (STP)
cable.
2) Perform the communication setup (select “DY” or “ST”, select the “ETHERNET” mode, and set
the 4th value of the IP address with the DIP switches. Refer to pages 19 to 21 for theprocedure.)
3) Set the base unit power switch to the ON position.

- 16 -

5.3 Communication Setup
This section explains how to set the Modbus (RS-485 or Ethernet) communication.

 Set the base unit power switch to the OFF position before using the DIP switches to avoid
incorrect operation or device failure.

 When the specifications of the connected Modbus master and those of this product do notmatch, it may cause incorrect operation (e.g. communication becomes disabled).

5.3.1

DIP Switches
This section explains how to operate the DIP switches.

 Set the base unit power switch to the OFF position before using the DIP switches to avoid
incorrect operation or device failure.
 Set the DIP switches in accordance with your selected communication method.

 Ensure that each switch is clearly set to the 1/0, DY/ST, and Ethernet/RS485 positions.
Unclear setting may result in incorrect operation or communication.

DIP switches are located in the upper part of the base unit

Base unit power switch- 17 -

Address plateWith address plate removed
DIP Switches
Item

Component

Description/function

Switches the IP address type between “DY” and “ST”.
DY: Dynamic IP address (DHCP)
ST: Static IP address
Switches the communication mode between “ETHERNET”
and “RS485”.
2
Mode change switch
ETHERNET: Modbus TCP (Ethernet)
RS485: Modbus RTU (RS-485)
Sets the address (unit ID) for this product.
Settable range: 1 (0000 0001) to 254 (1111 1110).
Address setting switches
3
The unit ID set here will also serve as the 4th value of the IP(8 places)
address when Modbus TCP (Ethernet) is selected with themode change switch.** If the 4th value is set to 0 (0000 0000) with the address setting switches, it will be superseded by
the value set by a web browser.
1

IP address type switch

NOTE

The DIP switches are accessible when the address plate is removed. To remove theaddress plate, refer to 7-1. “Operation Procedure” of the PS-7-M series gas
detector’s instruction manual.

- 18 -

（1） Set the IP address type: “DY” or “ST”
Select the IP address type between “Dynamic” and “Static” by using the IP address type switch.
When “Dynamic” is selected, IP address will be automatically assigned to the detector.
The setting here is active when the “ETHERNET (Modbus TCP)” is selected with the mode changeswitch.

Each DIP switch enters the ON status when it is set to the ON position.

IP address type

DIP switch position (Switch No.1)

DY: Dynamic IP address (DHCP)ON

ST: Static IP address

OFF (by default when shipped out)

（2） Set the communication mode: “ETHERNET” or “RS485”
Select the Modbus communication mode between “ETHERNET” and “RS485” by using the modechange switch.

Each DIP switch enters the ON status when it is set to the ON position.

Communication mode

DIP switch position (Switch No. 2)

ETHERNET: Modbus TCP

ON (by default when shipped out)

RS485: Modbus RTU (RS-485)

OFF- 19 -

（3） Set the address (Unit ID)
The address set using the address setting switches is the unit ID. In case of Modbus TCP (Ethernet),
the unit ID also serves as the 4th value of the IP address.
Set the address by taking the following steps.

 Do not use the address “255 (1111 1111)”, because the communication will be disabled.

 The address can be set to any value within the settable range, but if the same address isused by more than one unit (detector), the relevant units cannot communicate.
Address setting switches (left eight DIP switches)

1
0
Set the address by sliding the eight address setting switches to the “1” or “0” positions.
The 8-digit number is an 8-bit binary number representing the address.
The address settable range is 1 (0000 0001) to 254 (1111 1110).
Set value
0 (0000 0000)

1 (0000 0001) to
254 (1111 11110)

NOTE

Description
Invalid address
Modbus RTU (RS-485): Do not use the address “0 (0000 0000)”, because
the relevant units cannot communicate.
Modbus TCP (Ethernet): If the address is set to “0 (0000 0000)” with theaddress setting switches, it will be superseded by the value set by a web
browser.
Valid address
Modbus RTU (RS-485): The address represents the unit ID.
Modbus TCP (Ethernet): The address represents the 4th value of the IP
address.

Refer to the PS-7-M IP address setting guide (separate document) for how tochange the IP address with a web browser.

- 20 -

A. Modbus RTU (RS-485) communication address setting
When the mode change switch is in the “RS485” position, the address set for Modbus RTU(RS-485) communication will supersede. The set address represents the unit ID.
Set the Unit ID with the address setting switches.

NOTE

Up to 32 units, including a master, can be connected on a Modbus RTU (RS-485)
network. Set the unit IDs (from 1 to 254) for a maximum of 31 slaves (detectors).

For example, if you want to set the unit ID to “100”, set the address setting switches to the“0110 0100” positions. “0110 0100” is an 8-bit binary number equivalent to “100” in decimal.

B. Modbus TCP (Ethernet) communication address setting
When the mode change switch is in the “ETHERNET” position and the IP address type switch
is in the “ST (static IP address)” position, the address set for Modbus TCP (Ethernet)
communication will supersede. The set address represents the 4th value of IP address.
Set the 4th value of IP address with the address setting switches.
The default IP address when shipped out is “192.168.100.1”.
For example, if you want to set the IP address of the detector to “192.123.45.10”, take thefollowing steps.
(1) Set the first three values of the IP address to “192.123.45” from a web browser.
(2) Set the address setting switches to the “0000 1010” positions. The 4th value of the IP
address will be set to “10”. “0000 1010” is an 8-bit binary number representing “10”.

NOTE If the address is set to “0 (0000 0000)” with the address setting switches, it will
be superseded by the value set by a web browser.

 Refer to the PS-7-M IP address setting guide (separate document) for how tochange the IP address with a web browser.

- 21 -

5.3.2

Status LEDs
The status LEDs located on the base unit indicate the LAN cable and communication statuses.
Address plate

Status LEDs 1 to 3

With address plate removed

Component

LED No.

Green
Status LEDs

1
2

3

Description
When lit, a LAN cable is securely connected to the RJ-45 jack and aswitching hub
When flashing, Ethernet or RS-485 communication is in progress
Communication status between the base unit and main unit When flashing, communication is normal (transmitting and receiving
are in progress)
 When steady, no response from the main unit (no receiving) When not lit, no request from the base unit (no transmitting)- 22 -

6 Communication Protocol
This chapter describes the communication protocol.
1. Modbus communication protocol overview
2. Function codes and their functions
3. Response in the event of an error
4. Message examples
5. Register address map- 23 -

6.1 Modbus Communication Protocol Overview
Modbus communication uses a single-master-multiple-slave configuration.
In Modbus communication, a transaction is always initiated by a master, in which the master sends
a request message then a slave returns a response message.

6.1.1

Message Configuration
A Modbus message frame consists of the following four items: unit ID (IP address), function code,
data and error check code. They are transmitted in the following sequence.
Item(1) Address(2) Function(3) Data(4) CRCNOTE

Message data
Unit ID (IP address)
Function code
Data
Error check code

Data size
1 byte1 byteVariable length of up to125 words (250 bytes)
2 bytes

Error check code is not included in Modbus TCP (Ethernet) message frame.

(1) Unit ID (IP address)
Only when the slave’s unit ID (IP address) and the one specified by the master match, the slave
will process the relevant request message. If they do not match, the slave will not respond to themaster.
In the Modbus RTU (RS-485) communication, the address set using the address setting
switches represents the Unit ID. In the Modbus TCP (Ethernet) communication, the address set
using the address setting switches represents the 4th value of the IP address.

NOTE

For how to set the address setting switches, refer to (3) “Set the address” of 5.3.1“DIP Switches”.

 Do not use the address “255 (1111 1111)”, because the communication will be disabled.

 The address can be set to any value within the settable range, but if the same address isused by more than one unit (detector), the relevant units cannot communicate.
(2) Function code
The function code tells the slave what kind of action to perform. The slave (this detector) willtake action specified by the function code it supports. After the slave performs the specified
action normally, it will return a response message including the same function code.

NOTE Refer to 6.2 “Function Codes” for the function codes supported by this product.
 A register address to read from/write to will be assigned per function code.
 There are four types of registers: coil, input status, input register, and holding
register. The address range to read from/write to differs depending on theregister type.
 All Modbus registers where this detector’s data items are saved per function
code supported by this detector, are holding registers.
 Holding register address range is from 40001 to 49999 on the Modbus protocol.
This detector’s data (e.g. gas concentrations, device setup details) will beallocated in this range.

- 24 -

(3) Data
This is necessary data for a slave to take action based on the function code. The data
configuration differs depending on the function code. It consists of a starting register address,
quantity of data, or write data, etc.
Data is variable length of up to 125 words (250 bytes).

NOTE Refer to 6.2 “Function Codes” for the function codes supported by this product.
 The maximum data size differs depending on the function code.

(4) Error check code (for Modbus RTU only)
A Modbus RTU (RS-485) message contains an error check code (CRC value) calculated by the
CRC-16 method to detect a request/response message error.
The data size of a CRC value is 2 bytes, and they are sent by the byte in the sequence of
low-order byte followed by high-order byte.
CRC-16 calculation uses data items from unit ID through the one before the error check code(the end of the Data).
The slave calculates a CRC value based on a received request message, then compares it with
the CRC value (error check code) contained in the message. If they do not match, no responseis returned and no action taken.

NOTE

Refer to 6.1.2 “CRC-16 Calculation” for CRC-16.

- 25 -

6.1.2

CRC-16 Calculation (for Modbus RTU only)This section describes the CRC-16 calculation method for Modbus RTU (RS-485).
CRC-16 generation method (polynomial: X16＋X15＋X2＋1)
1. Initialize the CRC register (2-byte error check code) to FFFF in hex.
2. XOR the 1st letter (1 byte) of the received data with the lower-order byte of the CRC register andstore the XOR-result in the CRC register.
3. Save the LSb (0th bit) value of the CRC register.
4. Right-shift the CRC register by one bit (toward the LSb).
5. If the value saved at step 3 above is “1”, XOR the CRC register with the generator polynomial“A001 (hex)” (1010 0000 0000 0001), then store the result in the CRC register.
6. Repeat the process (steps 3 to 5) 7 times.
7. Repeat the process (steps 2 to 6) on the 2nd letter of the received data or later until the end of
the received data (CRC is excluded).
8. The value that remains in the CRC register is the final CRC value.
The generated CRC value is compared with the CRC value (error check code) contained in therequest message from the master. If they match, the slave will take action according to the request
and create a response message. If they do not match, the slave will not take any action or send a
response message.
The slave includes the generated CRC value (2-byte error check code) in a response message thensends it by the byte in the sequence of low-order byte followed by high-order byte.

NOTE

6.1.3

In the Modbus RTU (RS-485) communication, if no response is returned from theslave (this detector), the master must check that the error check code (CRC value)
contained in the request message is correct.

Communication Procedure
This section describes the Modbus communication procedure.
(1) The master sends a request message to the slave (this detector).
(2) The slave checks if the unit ID (4th value of the IP address in case of Modbus TCP) contained in
the request message matches its own unit ID ((4th value of the IP address). The master canstart Modbus communication individually with individual slaves which exist on the same networkby specifying the unit ID (4th value of the IP address in case of Modbus TCP).
MasterSlave
Request message
Command

Response message
Data(3) If there is a match, the slave takes action according to the contents of the request message andcreates a response message. If the slave detects an error, it creates an exception response
message including an exception code.

NOTE

Refer to 6.4.5 “Exception Response” for the message configuration in the event ofan error.

- 26 -

(4) If there is no match, the slave discards the request message, then waits for a next request
message (non-response status).
(5) After sending a request message, the master checks if it receives a response from the slave.
If there is no response or exception response message (exception code), the master will
perform a communication error process.
MasterSlave
Request message
Command

No response

Response message
Command

Response message
Exception code

- 27 -

6.1.4

Modbus RTU Communication IntervalThis section describes the Modbus RTU (RS-485) communication interval.

Current request

Data

Start

Unit
ID

Idlingtime(>3.5
letters)▲ Previous response message

Function
code

Data

CRC(L)

CRC(H)End

Data

Idlingtime(>3.5
letters)▲Error check code

▲Current response message

Provide a non-communication interval (idling time of more than 3.5-letter) between message
frames, to identify the end and start of each message.
The slave returns a response message after non-communication interval (idling time of more than
3.5-letter) from its receipt of a request message.
If a space of more than 3.5 letters is detected within a message frame, the slave judges that themessage frame ends then discards the message, then judges the next received data to be thestart of the request message.

NOTE

Idling time calculation method
For example, when the communication speed is 9600bps and 1 letter is 11-bit long
(Modbus RTU communication data),
Interval per letter = 1 /9600 x 11 x 1000 ≈ 1.15 msec.
If converted to 3.5 letters, 1.15 x 3.5 ≈ 4.01 msec.

- 28 -

6.1.5Differences between Modbus TCP and Modbus RTU Protocols
This section describes the differences between Modbus TCP (Ethernet) and Modbus RTU (RS-485)
communication protocols.
① Transaction identifier = TRXN ID (data size: 2 bytes)
In Modbus TCP communication, the exact value set in the request message (arbitrary) will be
included in a response message.
② Protocol identifier = Protocol ID (data size: 2 bytes)
Fixed at “0”.
③ Field length (data size: 2 bytes)
Quantity of transferred data from ④ to ⑦
④ Address/Unit identifier (data size: 1 byte)
This is unit ID for Modbus RTU and the 4th value of IP address for Modbus TCP.
⑤ Function code (data size: 1 byte)
Function code supported by this detector.
⑥ Data (data size: variable length)
Message (data) corresponding to the function code.
⑦ Error check code (CRC) (data size: 2 bytes)
CRC value calculated by the CRC-16 method.

NOTE

Message configurations from ④ to ⑥ are common between Modbus TCP and
Modbus RTU.

- 29 -

6.2 Function Codes
The following table lists the function codes supported by this product.
Maximum
data size(words)Function code
Function
Code

Hex

03

0x03

06

0x06

16

0x10

23

0x17

NOTE

Read single/multiple
holding registers
Write single holding
registerWrite multiple holding
registers
Read and write multiple
holding registers

125
125
123
125 (read)
121 (write)

Remarks- Holding register address
range: 40001-49999- Gas concentrations,status information, anddevice setup details
including gas/trouble
alarm related setups

 Register data access unit is 16 bits data length (1 word).
 Function code 23 (0x17) applies to Modbus TCP (Ethernet) only.

 Register address range used by this detector to save its data: 40001 to 41321.

- 30 -

6.3 Response in the Event of an Error
This section describes the response in the event of a Modbus communication error.
If the slave (this detector) judges that there is an error with a request from the master, the slave will
create an exception response message and send it to the master without processing the request.
If an exception response message is returned from the slave, the master should be capable ofchecking its contents.
In the Modbus RTU (RS-485) communication, if a communication error, listed in the table below,
occurs, the slave will not return an exception response message and wait for the next request.
Error

Description

Framing error

The stop bit of the received data cannot be detected

Overrun error

In the RS-485 communication, before reading the received data from thereceived data register, the next one frame of data was received

Parity error

The parity bit of the received data cannot be detected

CRC error

The error check codes (CRC values) do not match- 31 -

6.3.1

Error Codes (Exception Codes)
The following table lists error codes (exception codes) supported by this detector.
CodeError name

Cause

0x01

Illegal function code

A received function code is not the one supported by this detector

0x02

Illegal address error- A received Modbus register address is not the one defined bythis detector- Writing was performed to a read-only register

0x03

Illegal data error

Invalid data (data not defined by the detector) was written

0x04

Slave device error

A communication timeout error occurred between the main unit
and base unit, including the main unit’s power-off

0x06

Slave device busy

The slave received a request, while it is still processing aprevious request (slave is in a busy state)

0x07

NOTE

Negative acknowledge

The read/write data size of a request message is 0 or exceeds(NACK)

the maximum limit (125 words)

 Refer to 6.2 “Function Codes” for the function codes supported by this product.
 The maximum data size differs depending on the function code.
 If the specified read/write starting register address falls in the reserved area, anillegal address error occurs. However, even if reserved area is included in thespecified addresses to read from/write to, excluding the read/write starting
register address, an Illegal address error does not occur.
If data is read from/written from/to register address 41321 and after, an illegal
address error occurs. Writing to the reserved area or read-only register isinvalid.
*Reserved area: registers not defined by the detector

 Data read from the reserved area or write-only registers is “0xFFFF” (wordsize).

- 32 -

6.4 Message Examples
This section provides examples of request/response messages per function code supported by thisdetector, and an example of exception response message in the event of an error.
6.4.1

Function Code 03 (Read Single/Multiple Holding Registers)
Function code 03 (0x03) is used to read the data from the specified register addresses.
Example of request message
The master sends function code 03 (0x03) to the slave (unit ID = 01) in order to read two words ofdata from register address 41039 (relative address = 1038 (0x040E)). The current gas concentration
and F.S. code will be read from register addresses 41039 and 41040.
Message frame
Data itemData
size(byte)TRXN ID
Hi 2
LoProtocol ID
Hi 2
Lo

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)

0
0
0
0

0x00
0x00
0x00
0x00

–
–
–
–

–
–
–
–

–
–
–
–

Hi
Lo

2

(5)
(6)

6

0x00
0x06

–
–

–
–

–
–

Unit ID
Function code
StartingHi
address
Lo

1
1
2

(7)
(8)
(9)
(10)

1
3
1038

0x01
0x03
0x04
0x0E

(1)
(2)
(3)
(4)

1
3
1038

0x01
0x03
0x04
0x0E

Quantity ofregisters to
be readError check
data

Hi
Lo

2

(11)
(12)

0
2

0x00
0x02

(5)
(6)

0
2

0x00
0x02

Lo
Hi

2

–
–

–
–

–
–

(7)
(8)

Quantity ofcomm. data

Common to both Modbus TCP and Modbus RTU.

- 33 -

0xA4
0xF8

Remarks

Modbus TCP
only
Modbus TCP
only
Fixed at “00”.
Modbus TCP
only
Number of data
which follows
unit ID

Read starting
register address
Read by theword
Range: 1–125
Modbus RTU
only

Example of response message
The slave returns a response message including the “current gas concentration = 25%F.S. (0x0019)
and F.S. code = 101 (0x0065)” to the master.
Message frame
Data itemData
size(byte)TRXN ID
Hi
2
Lo
Protocol
Hi
2
ID
Lo

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)

0
0
0
0

0x00
0x00
0x00
0x00

–
–
–
–

–
–
–
–

–
–
–
–

Hi
Lo

2

(5)
(6)

13

0x00
0x0D

–
–

–
–

–
–

Unit ID
Function code
Quantity of data

1
1
1

(7)
(8)
(9)

1
3
4

0x01
0x03
0x04

(1)
(2)
(3)

1
3
4

0x01
0x03
0x04

Data1

Hi
Lo
Hi
Lo

2

(10)
(11)
(12)
(13)

25

0x00
0x19
0x00
0x65

(4)
(5)
(6)
(7)

25

0x00
0x19
0x00
0x65

Lo
Hi

2

–
–

–
–

–
–

(8)
(9)

Quantityof comm.
data

Data2

Error
check
data

2

101

Common to both Modbus TCP and Modbus RTU.

- 34 -

101

0x2B
0x4A

Remarks

Modbus TCP
only
Modbus TCP
only
Fixed at “00”Modbus TCP
only
Number of data
which follows
unit ID

Quantity of
response data =N x 2 bytes
N: Quantity ofregisters
N range =1–125
Sent by the byte
in the sequenceof high-orderbyte followed
by low-orderbyte: Data 1, 2,
3, 4….
Modbus RTU
only6.4.2Function Code 06 (Write Single Holding Register)
Function code 06 (0x06) is used to write one word of data to the specified single register.
Example of request message
The master sends function code = 06 (0x06) to the slave (unit ID = 03). One word (2 bytes) of datafor “Host maintenance mode ON command” will be written to register address 40050 (relative
address = 49 (0x0031)).
Host maintenance mode ON command (with self-resetting) = ON (0x0011)
Message frame
Data itemData
size(byte)TRXN ID
Hi
2
Lo
Protocol
Hi
2
ID
Lo

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)

0
0
0
0

0x00
0x00
0x00
0x00

–
–
–
–

–
–
–
–

–
–
–
–

Remarks

Modbus TCP
only
Modbus TCP
only
Fixed at “00”.
Modbus TCP
only
Number of data
which follows
unit ID

Hi
Lo

2

(5)
(6)

6

0x00
0x06

–
–

–
–

–
–

Unit ID
Function code
StartingHi
address
Lo

1
1
2

(7)
(8)
(9)
(10)

3
6
49

0x03
0x06
0x00
0x31

(1)
(2)
(3)
(4)

3
6
49

0x03
0x06
0x00
0x31

Write starting
register address

Data

2

(11)
(12)
–
–

17

0x00
0x11
–
–

(5)
(6)
(7)
(8)

17

0x00
0x11
0x19
0xEB

Write by theword.
Modbus RTU
only

Quantityof comm.
data

Error
check
data

Hi
Lo
Lo
Hi

2

–
–

Common to both Modbus TCP and Modbus RTU.

- 35 -Example of response message
The slave returns a response message (result) informing that “Host maintenance mode ON
command” (one word of data) has been written, to the master.
Host maintenance mode ON command (with self-resetting) = ON (0x0011)
Message frame
Data itemData
size(byte)TRXN ID
Hi
2
Lo
Protocol
Hi
2
ID
Lo

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)

0
0
0
0

0x00
0x00
0x00
0x00

–
–
–
–

–
–
–
–

–
–
–
–

Hi
Lo

2

(5)
(6)

13

0x00
0x0D

–
–

–
–

–
–

Unit ID
Function code
StartingHi
address
Lo

1
1
2

(7)
(8)
(9)
(10)

3
6
49

0x03
0x06
0x00
0x31

(1)
(2)
(3)
(4)

3
6
49

0x03
0x06
0x00
0x31

Data

2

(11)
(12)
–
–

17

0x00
0x11
–
–

(5)
(6)
(7)
(8)

17

0x00
0x11
0x19
0xEB

Quantityof comm.
data

Error
check
data

Hi
Lo
Lo
Hi

2

–
–

Common to both Modbus TCP and Modbus RTU.

- 36 -

Remarks

Modbus TCP
only
Modbus TCP
only
Fixed at “00”.
Modbus TCP
only
Number of data
which follows
unit ID

Write by theword.
Modbus RTU
only6.4.3Function Code 16 (Write Multiple Holding Registers)
Function code 16 (0x10) is used to write a block of contiguous data to the specified multiple
registers.
Example of request message
The master sends function code = 16 (0x10) to the slave (unit ID = 03). “Test mode ON command”
and “test gas concentration” will be written to register addresses 40048 (relative address = 47
(0x002F)) and 40049 (relative address = 48 (0x0030)) respectively.
Test mode ON command = ON (0x0001)
Test gas concentration = 25%F.S. (0x0019)
Message frame
Data itemData
size(byte)TRXN ID Hi
2
LoProtocol
Hi
2
ID
Lo

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)

0
0
0
0

0x00
0x00
0x00
0x00

–
–
–
–

–
–
–
–

–
–
–
–

Hi
Lo

2

(5)
(6)

11

0x00
0x0B

–
–

–
–

–
–

Unit ID
Function code
StartingHi
address
Lo

1
1
2

(7)
(8)
(9)
(10)

3
16
47

0x03
0x10
0x00
0x2F

(1)
(2)
(3)
(4)

3
16
47

0x03
0x10
0x00
0x2F

Quantityofregisters

２

(11)
(12)

2

0x00
0x02

(5)
(6)

2

0x00
0x02

1

(13)

4

0x04

(7)

4

0x04

2

(14)
(15)
(16)
(17)
–
–

1

0x00
0x01
0x00
0x19
–
–

(8)
(9)
(10)
(11)
(12)
(13)

1

0x00
0x01
0x00
0x19
0x2A
0x45

Quantityof comm.
data

Hi
Lo

Quantity of
data

Data1
Data2
Error
check
data

Hi
Lo
Hi
Lo
Lo
Hi

2
2

25
–
–

Common to both Modbus TCP and Modbus RTU.

- 37 -

25

Remarks

Modbus TCP
only
Modbus TCP
only
Fixed at “00”.
Modbus TCP
only
Number of data
which follows
unit ID

Write starting
register address
Quantity ofregisters to be
writtenRange: 1–123
Quantity of data
= N x 2 bytes
N: Quantity ofregisters
Write data by
the word

Modbus RTU
only

Example of response message
The slave returns a response message (result) informing that contiguous data has been written to
multiple registers, to the master.
Message frame
Data itemData
size(byte)
TRXN
Hi
2
ID
Lo
Protocol Hi
2
ID
Lo

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)

0
0
0
0

0x00
0x00
0x00
0x00

–
–
–
–

–
–
–
–

–
–
–
–

Hi
Lo

2

(5)
(6)

13

0x00
0x0D

–
–

–
–

–
–

unit ID
Function code
StartingHi
address Lo
Quantity HiofLo
registers

1
1
2

(7)
(8)
(9)
(10)
(11)
(12)

3
16
47

0x03
0x10
0x00
0x2F
0x00
0x02

(1)
(2)
(3)
(4)
(5)
(6)

3
16
47

0x03
0x10
0x00
0x2F
0x00
0x02

Error
check
data

2

–
–

–
–

–
–

(7)
(8)

Quantity
of
comm.
data

Lo
Hi

2

2

Common to both Modbus TCP and Modbus RTU.

- 38 -

2

0x71
0xE3

Remarks

Modbus TCP
only
Modbus TCP
only
Fixed at “00”.
Modbus TCP
only
Number of data
which follows
unit ID

Write starting
register address
Quantity ofregisters to be
writtenRange: 1–123
Modbus RTU
only6.4.4

Function Code 23 (Read and Write Multiple Holding Registers)
Function code 23 (0x17) is used to perform a combination of one read operation and one write
operation. A block of contiguous data will be written to specified multiple registers, then a block ofcontiguous data will be read from specified multiple registers. The write operation is performed
before the read.

NOTE

Function code 23 (0x17) applies only to Modbus TCP (Ethernet) and it does not
apply to Modbus RTU (RS-485)

Example of request message
The master sends function code = 23 (0x17) to the slave (unit ID = 05). Two words of data (current
gas concentration and F.S. code) starting from register address 41039 (relative address = 1038
(0x040E)) will be read, then two words of data (Test mode ON command and test gas concentration)
will be written to register addresses 40048 (relative address = 47 (0x002F)) and 40049 (relative
address = 48 (0x0030)) respectively.
Test mode ON command = ON (0x0001)
Test gas concentration = 25%F.S. (0x0019)
Message frame
Data itemData
size(byte)
TRXN
Hi
2
ID
Lo
Protocol Hi
2ID
Lo
Quantity Hi
2
of
Lo
comm.
data
Unit ID
1
Function code
1
Read
Hi
2
startingLoaddress２
Quantity HiofLo
registers
to be
read
Write
Hi
2
startingLoaddress
Quantity Hi
2ofLo
registers
to bewritten
Quantity of data 1

Modbus TCP
No.
Byte
Hex
data

No.

(1)
(2)
(3)
(4)
(5)
(6)

0
0
0
0
11

0x00
0x00
0x00
0x00
0x00
0x0B

–
–
–
–
–
–

–
–
–
–
–
–

–
–
–
–
–
–

(7)
(8)
(9)
(10)

3
16
1038

0x03
0x10
0x00
0x2F

–
–
–
–

–
–
–

–
–
–
–

(11)
(12)

2

0x00
0x02

–
–

–
–

–
–

(13)
(14)

47

0x00
0x2F

–
–

–
–

–
–

(15)
(16)

2

0x00
0x02

–
–

–
–

–
–

Range: 1–121

(17)

4

0x04

–

–

–

Quantity of data
= N x 2 bytes
N: Quantity ofregisters- 39 -

Modbus RTU
Byte
Hex
data

Remarks

Fixed at “00”.
Number of data
which follows
unit ID

Range: 1–125

Message frame
Data itemData
size(byte)

Modbus TCP
No.
Byte
Hex
data

No.

Data1

(18)
(19)
(20)
(21)
–
–

–
–
–
–
–
–

Data2
Error
check
data

Hi
Lo
Hi
Lo
Lo
Hi

2
2
2

1
25
–
–

0x00
0x01
0x00
0x19
–
–

Modbus RTU
Byte
Hex
data

–
–
–
–

–
–
–
–
–
–

Remarks

Write by theword

Example of response message
The slave returns a response message including the “current gas concentration = 25%F.S. (0x0019)
and F.S. code = 101 (0x0065)” to the master.
Message frame
Data itemData
size(byte)
TRXN
Hi
2
ID
Lo
Protocol Hi
2ID
Lo
Quantity Hi
2
of
Lo
comm.
data
Unit ID
1
Function code
1
Quantity of
1
data

Data1
Data2

Error
check
data

Hi
Lo
Hi
Lo

2

Lo
Hi

2

2

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)
(5)
(6)

0
0
0
0
13

0x00
0x00
0x00
0x00
0x00
0x0D

–
–
–
–
–
–

–
–
–
–
–
–

–
–
–
–
–
–

(7)
(8)
(9)

1
3
4

0x01
0x03
0x04

–
–
–

–
–
–

–
–
–

(10)
(11)
(12)
(13)

25

0x00
0x19
0x00
0x65

–
–
–
–

–

–
–
–
–

–
–

–
–

–
–

–
–

–
–

101

- 40 -–––

Remarks

Fixed at “00”.
Number of data
which follows
unit ID

Quantity of
response data =N x 2 bytes
N: Quantity ofregisters
N range= 1–125
Sent by the byte
in the sequenceof high-orderbyte followed
by low-orderbyte: Data 1, 2,
3, 4….

6.4.5

Exception Response (Response in the event of an error)
When an error (e.g. communication error. Refer to 6.3.1 Error Code for details of errors) occurs, theslave sends an exception response to the master in the following configuration. In an exception
response, the slave sets the most-significant bit (MSb) of the function code to “1 (generated byadding 0x80 to the received function code)” and uses it as an error function code.
(1) Unit ID: 1 byte
(2) Error function code: 1 byte
(3) Exception code (error code): 1 byte
(4) Error check code: 2 bytes
Example of error function code generation
When an error occurs while receiving a request message whose function code is “0x06”, 0x80 will
be added to the function code to form an error function code: 0x80＋0x06 = 0x86.
The generated error function code will be added to an exception response.

NOTE

Refer to 6.1.2 “CRC-16 Calculation” for error check codes.

Example of transactions in the event of an error is as follows.
Example of request message
The master sends function code = 16 (0x10) to the slave (unit ID = 03).
The request specifies the non-existent register address 40100 (relative address = 99 (0x0063)) andnumber of registers to be written.
Example of response message
The slave returns the following exception response message to the master.
Message frame
Data itemData
size(byte)
TRXN
Hi
2
ID
Lo
Protocol Hi
2ID
Lo
Quantity Hi
2
of
Lo
comm.
data
Unit ID
1
Error function1
code
Error code
(Exception
code)
Error
Lo
check
Hi
data

No.

Modbus TCP
Byte
Hex
data

No.

Modbus RTU
Byte
Hex
data

(1)
(2)
(3)
(4)
(5)
(6)

0
0
0
0
3

0x00
0x00
0x00
0x00
0x00
0x03

–
–
–
–
–
–

–
–
–
–
–
–

–
–
–
–
–
–

(7)
(8)

3
144

0x03
0x90

(1)
(2)

3
144

0x03
0x90

1

(9)

2

0x02

(3)

2

0x02

2

–
–

–
–

–
–

(8)
(9)

Common to both Modbus TCP and Modbus RTU.

- 41 -

0x6C
0x01

Remarks

Modbus TCP only
Modbus TCP only
Fixed at “00”.
Modbus TCP only
Number of data
which follows unit
ID
“0x80” is added to
the received
function code“0x10”
Illegal address error

Modbus RTU only

6.5 Register Address Map
This section describes the register address map for the data used by this detector.
The detector assigns its data (e.g. gas concentrations, status information, device setup details) to its holding
registers. A request message from the master specifies the register addresses to read from/write to.
Modbus Register Address Map

40001

Relativeaddress
(hex)
0

40002

Registeraddress

Read (R) or
Write (W)

Data
type

Flow rate

R

Word

1

AL1 set value

R

Word

40003

2

AL2 set value

R

Word

40004

3

Alarm mode
combination

R

Word

40005

4

AL1 delay time

R

Word

40006

5

AL2 delay time

R

Word

40007

6

Zero suppression
value (21vol%suppression value
for oxygen)

R

Word

40009

8

Target gas (1stand 2nd letters)

R

Word

Register name

Data contents
Read current flow rate
Response example: 0x01F4 when flowrate is measured at 500ml
Read AL1 set value
Response example: 0x0019 when AL1
set value is 25%F.S.
Read AL2 set value
Response example: 0x0028 when AL2
set value is 40%F.S.
Read alarm mode combination
0: High-High limit 0x0000
1: Low-Low limit 0x0001
2: High-Low limit 0x0002
Read AL1 delay time
Response example: 0x0005 when delay
time is 5 sec
Read AL2 delay time
Response example: 0x0005 when delay
time is 5 sec
Read zero suppression value
Response example: 0x0019 when
suppression value is 25%

Read target gas
Target gas (max. 4 letters) are set in hex
ASCII code.
Response example: When target gas isrdCO2, 1st letter “C”, 2nd letter “O” and 3
letter “2” are returned in hex ASCII code

40010

40011

9

A

Target gas (3rdand 4th letters)

Measurement unit
code

R

Word

R

Word

- 42 -“C”: 0x43 (high-order byte of word data)“O”: 0x4F (low-order byte of word data)“2”= 0x32 (high-order byte of word data)“(space)” = 0x20 (low-order byte of worddata)
When gas name exceeds 5 letters, first
4 letters will be returned.
Read unit code for sensor unit
0: (None)
10: ppm
20: ppb
30: %Register
address

Relativeaddress(hex)

Register nameRead (R) or
Write (W)

Data
type

Data contents
40: %LEL

40013

C

40014

D

40015

E

Sensor unit Mfg.
No.(1st and 2ndletters)
Sensor unit Mfg.
No.(3rd and 4th
letters)
Sensor unit Mfg.
No. (5th and 6th
letters)
Sensor unit Mfg.
No.(7th and 8th
letter)R

Word

Read sensor unit Mfg. No. (8-letter
ASCII code)

R

Word

R

Word

Response example: When Mfg. No.
is ”C302026”, 1st letter is “C”, 2nd is “3”,3rd is “0, …. 7th is “6” and 8th is“(space)”R

Word“C”=0x43 (high-order byte of word data)“3”= 0x33 (low-order byte of word data)“0”= 0x30 (high-order byte of word data)“2”= 0x32 (low-order byte of word data)“0”= 0x30 (high-order byte of word data)“2”= 0x32 (low-order byte of word data)“6”= 0x36 (high-order byte of word data)“(space)”= 0x20 (low-order byte of word
data)
Read current test mode status
ON: 0x0001
OFF: 0x0000
Read test gas concentration value
Response example: 0x0019 when test
gas concentration is 25%
Read sensor current value
Range: 2.00 to 6.00 mA
Multiplied by 100, then converted to hex
to create the data to send.
Response example: 0x00C8 in case of
200 (2.00 mA)
Read sensor unit f-value (4 letter hex
ASCII)
Multiplied by 100, then converted to hex
to create the data to send.
Response example: 0x064 in case of
100 (f-value is 01.00)
Read calibration gas code (3-letter
ASCII code)
Response example: “0x2D”, “0x2D”,“0x2D” and “0x20” when code is - - plus space.

40016

F

40017

10

Test mode on/off

R

Word

40018

11

Test gas
concentration

R

Word

40019

12

Sensor current
value

R

Word

40020

13

f-value

R

Word

40021

14

R

Word

40022

15

R

Word

40023

16

Calibration gas
code (1st and 2ndletters)
Calibration gas
code (3rd and 4th
letters)
Calibration gas
concentration

R

Word

Read calibration gas concentration
value
Response example: 0x004B when thegas concentration value is 75%

40025

18

Linear table X1Y1

R

Word

Read linear table (X1,Y1)
Response example:
When X1 = 20%, 0x0014 (high-orderbyte of word data)- 43 -

Register
address

Relativeaddress(hex)

Register nameRead (R) or
Write (W)

Data
type

40026

19

Linear table X2Y2

R

Word

40027

1A

Linear table X3Y3

R

Word

40028

1B

Linear table X4Y4

R

Word

40029

1C

Linear table X5Y5

R

Word

40030

1D

Linear table X6Y6

R

Word

40031

1E

Main unit software
version

R

Word

40032

1F

Base unit software
version

R

Word

40048

2F

Test mode on/off

W

Word

40049

30

W

Word

40050

31

Test gas
concentration
Host maintenancemode on/off

W

Word

- 44 -

Data contents
When Y1 = 20%, 0x0014 (low-orderbyte of word data)
Read linear table (X2,Y2)
Response example:
When X2 = 40%, 0x0028 (high-orderbyte of word data)
When Y2 = 40%, 0x0028 (low-orderbyte of word data)
Read linear table (X3,Y3)
Response example:
When X3 = 50%, 0x0032 (high-orderbyte of word data)
When Y3 = 50%, 0x0032 (low-orderbyte of word data)
Read linear table (X4,Y4)
Response example:
When X4 = 60%, 0x003C (high-orderbyte of word data)
When Y4 = 60%, 0x003C (low-orderbyte of word data)
Read linear table (X5,Y5)
Response example:
When X5 = 80%, 0x0050 (high-orderbyte of word data)
When Y5 = 80%, 0x0050 (low-orderbyte of word data)
Read linear table (X6,Y6)
Response example:
When X6 = 90%, 0x005A (high-orderbyte of word data)
When Y6 = 90%, 0x005A (low-orderbyte of word data)
Read PS-7-M main unit software
versionResponse example: In case of ver.1.12,
112 = 0x0070
Read PS-7-M base unit software
versionResponse example: In case of ver.1.10,
110 = 0x006E

Set test mode to on/off
ON: 0x0001
OFF: 0x0000
Set test gas concentration value
Write example: 0x0019 to set to 25%
Set host maintenance mode to on/off
OFF: 0x0000
ON: 0x0001 (without self-resetting)
ON: 0x0011 (with 10-min
self-resetting)

Register
address

Relativeaddress(hex)

Register nameRead (R) or
Write (W)

Data
type

Data contents
Host maintenance mode is equivalent tomaintenance mode 1, and maintenancemode 2 is prioritized
Set AL1 set value
Write example: 0x0019 to set to25%F.S.
Always %F.S. is used
Set AL2 set value
Write example: 0x0028 to set to
40 %F.S.
Always %F.S. is used
Set alarm mode combination
0: High-High limit 0x0000
1: Low-Low limit
0x0001
2: High-Low limit 0x0002
Set AL1 delay time
Write example: 0x0005 to set to 5 sec
Set AL2 delay time
Write example: 0x0005 to set to 5 sec
Set zero suppression value
Write example: 0x0005 to set to 5%

40051

32

AL1 set value

W

Word

40052

33

AL2 set value

W

Word

40053

34

Alarm mode
combination

W

Word

40054

35

AL1 delay time

W

Word

40055

36

AL2 delay time

W

Word

40056

37

W

Word

40057

38

Zero suppression
value (21vol%suppression value)
Calibration gas
concentration

W

Word

Set calibration gas concentration value
Write example: 0x004B to set to 75%

40516

203

Current value(device status
information)

R

Word

Read current device status informationand gas/trouble alarms
Status byte 1
b7: Symbol for gas concentration value(0:＋/1:－)b6: (Reserved)
b5: Low flow rate 1 (0:Good/1:Not good)
b4: Low flow rate 2 (0:Good/1:Not good)b3: Broken pyrolyzer wire (0: Good/1:
Not good)b2: Sensor fault (0: Good/1: Not good)
b1: AL1 (0: OFF/1: ON)
b0: AL2 (0: OFF/1: ON)
Status byte 2
b7: Device setup change(0: No change/ 1: Change)b6: (Reserved)b5: (Reserved)
b4: Host maintenance mode
(0: OFF/1: ON)
b3: (Reserved)
b2: Test mode (0: OFF/1: ON)
b1: Maintenance mode 2 (0:OFF/1:ON)
b0: Maintenance mode 1 (0:OFF/1:ON)- 45 -

Register
address

Relativeaddress(hex)

Register nameRead (R) or
Write (W)

Data
type

Data contents

Response example: When AL1 and AL2
activate while in MNT2,
Status byte 1: 0x03 (high-order byte ofword data)
Status byte 2: 0x02 (low-order byte ofword data)

41039

40E

Current value(gas
concentration)

R

Word

41040

40F

F.S. code

R

Word

41284

503

Modbus settingchange permit

R/W

Word

Permission for Modbus setting change

41291

50A

Dynamic IP
address(high-order)

R

Word

41292

50B

Dynamic IP
address(low-order)

R

Word

41293

50C

R

Word

41294

50D

R

Word

41295

50E

R

Word

41296

50F

R

Word

Read currently-set default gateway(low-order), which is assigned to DHCP

41297

510

DHCP subnet
mask (high-order)
DHCP subnet
mask (low-order)
DHCP default
gateway(high-order)
DHCP default
gateway(low-order)
TCP/IP port No.

Read currently-set IP address(high-order)
Dynamic IP address (high-order)
assigned to DHCP
Read currently-set IP address(low-order)
Dynamic IP address (low-order)
assigned to DHCP
Read currently-set subnet mask
(high-order), which is assigned to DHCP
Read currently-set subnet mask
(low-order), which is assigned to DHCP
Read currently-set default gateway(high-order), which is assigned to DHCP

R

Word

41298

511

R

Word

41299

512

Static IP address(high-order)
Static IP address

R

Word

Read TCP port number
Example: 0x01F6 when Modbus/TCP
port No. is 502 (static)
Read 1st and 2nd values of static IP
address (high-order)
Read 3rd and 4tth values of static IP- 46 -

Read current gas concentration value
Response example 1: 0x000A when thegas concentration is 10%.
Response example 2: 0x0005 with 1
being assigned to bit7 of status byte 1,
when gas concentration is –5%
Read F.S. code
F.S. code is returned in hex
Response example: 0x0065 when F.S.
code is 101
Master will then convert received code
to F.S. value by referring to full scalecode table (refer to 7.5 Full Scale
Codes)

Register
address

Relativeaddress(hex)

Register nameRead (R) or
Write (W)

Data
type

(low-order)

Data contents
address (low-order)
4th value of IP address is Unit ID, too

Subnet mask
(high-order)
Subnet mask
(low-order)
Default gateway(high-order)
Default gateway(low-order)
IP address type
(DY/ST)R

Word

The 4th value of IP address is set withaddress setting switches (DIP
switches). It is valid if set to 1 to 254, but
invalid if set to 255. If set to 0 with theswitches, it will be superseded by theone set by high-order device (webbrowser)
Read subnet mask (high-order)

R

Word

Read subnet mask (low-order)

R

Word

Read default gateway (high-order)

R

Word

Read default gateway (low-order)

R

Word

MAC address (1stand 2nd bytes)
MAC address (3rdand 4th bytes)
MAC address (5thand 6th bytes)
Communication
speed

R

Word

R

Word

R

Word

R

Word

51C

Data length

R

Word

41310

51D

Stop bit

R

Word

41311

51E

Parity bit

R

Word

41312

51F

Unit ID

R

Word

Read IP address type (dynamic or
static), which is set with IP address typeswitch.
0x0000: Dynamic IP address
0x0001: Static IP address
Read MAC address (1st and 2nd bytes)of PS-7-M base unit
Read MAC address (3rd and 4th bytes)of PS-7-M base unit
Read MAC address (5th and 6th bytes)of PS-7-M base unit
Read Modbus RTU (RS-485)
communication speed (bps)Response example: 0x2580 in case of
9600 bps
Read Modbus RTU (RS-485) data
lengthResponse example: 0x0008 in case of
8 data bit length
Read Modbus RTU (RS-485) data
lengthResponse example: 0x0001 in case of 1
stop bit
Read Modbus RTU (RS-485) data
lengthResponse example:
0x0000: No parity
0x0001: Even parity
0x0010: Odd parity
Read unit ID set with address setting
switches (DIP switches)

41300

513

41301

514

41302

515

41303

516

41304

517

41305

518

41306

519

41307

51A

41308

51B

41309

- 47 -

41316

Relativeaddress
(hex)
523

41317

524

Registeraddress

Read (R) or
Write (W)

Data
type

Static IP address(high-order)

W

Word

Static IP address(low-order)

W

Word

Register name

41318

525

Subnet mask
(high-order)

W

Word

41319

526

Subnet mask
(low-order)

W

Word

41320

527

Default gateway(high-order)

W

Word

41321

528

Default gateway(low-order)

W

Word

NOTE

Data contents
Set 1st and 2nd values of static IP
address (high-order)
Valid when “0x0001 (static IP)” is set at
register address 41304.
The first three values of IP address are
written to this register from high-orderdevice (web browser)
Set 3rd and 4tth values of static IP
address (low-order)
Valid when “0x0001 (static IP)” is set at
register address 41304.
The first three values of IP address are
written to this register from high-orderdevice (web browser)
The 4th value of IP address is set withaddress setting switches (DIP
switches). It is valid if set to 1 to 254, but
invalid if set to 255. If set to 0 with theswitches, it will be superseded by theone set by high-order device (webbrowser)
Set subnet mask (high-order)
Valid when “0x0001 (static IP)” is set at
register address 41304
Invalid if bits are set to 1, 0, 1 from highto low bit
Set subnet mask (low-order)
Valid when “0x0001 (static IP)” is set at
register address 41304
Invalid if bits are set to 1, 0, 1 from highto low bit
Set default gateway (high-order)
Valid when “0x0001 (static IP)” is set at
register address 41304
Set default gateway (low-order)
Valid when “0x0001 (static IP)” is set at
register address 41304

Data newly written to the registers addresses from 41316 to 41321 will not bereflected in the register address map until the detector is restarted.

- 48 -

7 Device Status Information
This chapter describes the device operation statuses during gas alarm, trouble alarm, test mode,and maintenance mode.

- 49 -

7.1 Gas Alarm Operation
If the gas concentration exceeds the gas alarm set value, the alarm contacts will activate after thealarm delay time, and the gas detector will enter the gas alarm status.
The master can detect a gas alarm by reading the device status information located at register
address 40516.
When the gas concentration falls below the gas alarm set value, the gas detector will automatically
return to its normal status (self-resetting).

NOTE

For gas alarm operation of the main unit, refer to 7-2 “Operation – Gas Alarm” of thePS-7-M series gas detector’s instruction manual.

The device status information (register address: 40516) is one word consisting of two bytes, Statusbyte 1 (high-order byte) and Status byte 2 (low-order byte).
The 1st stage gas alarm (AL1) is assigned to bit1 1 of Status byte 1 and the 2nd stage gas alarm(AL2) is assigned to bit 0 of Status byte 1, as shown below.

Gas alarm
1st stagegas alarm(AL1)

Bit assignment (gas alarms status)
Register
Register name
Data contents
address
Current value40516
0: OFF / 1: ON (alarm is activated)(device status
Status byte 1
information)
bit7

bit0

1
bit1: AL1
0: Alarm is absent / 1: Alarm is present
Status byte 1
bit7
bit0
1
bit0:AL2

2nd stagegas alarm(AL2)- 50 -

7.2 Trouble Alarm Operation (Fault Alarm Operation)
When this detector detects an internal failure, it will activate a trouble alarm.
The master can detect a trouble alarm of a slave (this detector) by reading the device status
information at register address 40516.
Trouble alarm will be automatically cleared, when a problem is removed (self-resetting).

NOTE

For the trouble alarm operation of the main unit, refer to 7-3 “Operation – Trouble
Alarm” of the PS-7-M series gas detector's instruction manual.

(1) Low flow rate
A minimum flow rate is not present.
There are two low flow rate patterns. When the flow rate is reduced due to a clogged filter orexcessive negative pressure, etc., the flow rate icon spins slowly (low flow rate 1). When the flowrate is too low, the icon stops spinning, “FLOW” is shown on the LCD and a low flow rate alarm
activates (low flow rate 2).

NOTE

For the information on the LCD, refer to 5-6 “LCD Indicator Icons” of the PS-7-M
series gas detector's instruction manual.

(2) Broken pyrolyzer wire (when detector uses a pyrolyzer)
A broken wire occurs.
(3) Sensor fault
The sensor’s zero level output is extremely low, or
A broken sensor wire occurs (applies to CHS-7 combustible gas sensor only).
The device status information (register address: 40516) is one word consisting of two bytes, Statusbyte 1 (high-order byte) and Status byte 2 (low-order byte).
The trouble alarms are assigned to bits 2 to 5 of Status byte 1 as shown below.

Troublealarm
Low flowrate

Bit assignment (trouble alarms)
Register
Register name
Data contents
address
Current value
40516
0: Good /1: Not good(device status
Status byte 1
information)
bit7
bit0
1
bit5: Low flow rate 1
Status byte 1
bit7
bit0
1
bit4: Low flow rate 2

Brokenpyrolyzer
wire

0: Good /1: Not good
Status byte 1
bit7

bit0
1
bit3:

Broken pyrolyzer wireSensor fault

0: Good /1: Not good
Status byte 1
bit7

bit0
1
bit2: Sensor fault- 51 -

7.3 Test Mode Setup and Operation
Press the TEST switch on the main unit with the test stick to enter the test mode. Each press of therecessed TEST switch will turn on and off the test mode. The test mode can be also turned on/off
from the master by setting the test mode register to on/off via Modbus communication.
“TEST” appears on the LCD of this detector while in the test mode. The test mode will automaticallyturn off 10 minutes later.

NOTE

To enter the test mode from the main unit, refer to 7-4 “Operation – Test Mode” of thePS-7-M series gas detector’s instruction manual

Register name
Test mode on/off

Test gas
concentration

Registers for test mode setting
Register
Data type
Data contents
address
40048
Word
Set test mode to on/off
ON: 0x0001
OFF: 0x0000
40049
Word
Set test gas concentration value
Example: “0x0019” to set the value to 25%
Settable range: 1 to 100%

The master can check the test mode on/off status and the test gas concentration value by reading
the device status information located at register address 40516. It can also check them by reading
register address 40017 for test mode and register address 40018 for test gas concentration
respectively.
The device status information (register address: 40516) is one word consisting of two bytes, Statusbyte 1 (high-order byte) and Status byte 2 (low-order byte).
The test mode is assigned to bit 2 of Status byte 2 as shown below.

Mode
Test mode

Register
nameCurrent value(device status
information)

Bit assignment (test mode)
Registeraddress40516
0: OFF
1: ON
Status byte 2
bit7

Data contents

bit01
bit 2: Test mode

While in test mode, the gas alarm contacts activate. If the gas alarm contacts are used tooperate the interlocks of the external devices, release the interlocks beforehand, as needed
to prevent a possible activation of the interlocks during the test mode, or enter the
maintenance mode before entering the test mode. (Refer to 7-5. “Operation – Maintenance
Mode” for more information).
Notify those concerned before starting the gas alarm test.

- 52 -

7.4 Maintenance Mode Setup and Operation
The maintenance switch on the front of the base unit can switch between two maintenancemodes, maintenance mode 1 (MNT1) and maintenance mode 2 (MNT2).
There are three maintenance modes in total, maintenance mode 1 (MNT1), maintenance mode 2(MNT2), plus host maintenance mode.
The operation of the host maintenance mode is the same as maintenance mode 1.

NOTE

For the setup and operation for maintenance modes 1/2, refer to 7-5 “Operation –Maintenance Mode” of the PS-7-M series gas detector’s instruction manual.

The host maintenance mode can be turned on/off from the master by setting the test mode
register to on/off via Modbus communication.
“MNT1” or “MNT2” appears on the LCD while in maintenance mode, and “MNT1” appears while
in host maintenance mode.
The host maintenance mode will automatically turn off 10 minutes later.

Register nameHost maintenancemode on/off

Register for host maintenance mode setting
Register
Data type
Data contents
address
40050
Word
Set host maintenance mode to on/off
OFF: 0x0000
ON: 0x0001 (without self-resetting)
ON: 0x0011 (with 10-min self-resetting)

The master can check the current maintenance mode status by reading the device status information
at register address 40516.
The device status information (register address: 40516) is one word consisting of two bytes, Statusbyte 1 (high-order byte) and Status byte 2 (low-order byte).
The maintenance mode is assigned to bits 0, 1 and 4 of Status byte 2 as shown in the following
table.

- 53 -

Bit assignment (maintenance mode)
Register
nameRegisteraddress

Current
value(devicestatusinformation)

40516

Mode
MNT1

MNT2

Data contents
0: OFF /1: ON
Status byte 2
bit70: OFF /1: ON
Status byte 2
bit7

Host
maintenancemode

0: OFF /1: ON
Status byte 2
bit7

Disabled(Fixed atOFF)

Troublealarm
open
collector
Disabled(Fixed at
ON)

Disabled(Fixed at
OFF)

Disabled(Fixed at
ON)

Disabled(Fixed at
OFF)

Disabled(Fixed at
ON)

Gas
alarm
contacts

bit0
1
bit0:
MNT 1

bit0
1
bit1:
MNT2

bit0
1
bit4:
Host maintenance mode

 While in maintenance mode, the status information of gas/trouble alarms is sent to the master
digitally. If the status information is used to operate the interlocks of the external devices,
release the interlocks beforehand, as needed to prevent a possible activation of the interlocks
during the maintenance mode.
 Trouble alarm will activate if the main unit power switch is set to the OFF position while in any
maintenance mode.

 The analog output may change when the main unit power switch is set to the OFF position.

 During normal operation (gas monitoring mode), ensure the maintenance switch is set to thecenter position and the host maintenance mode is off. Gas alarm contacts and trouble alarm
open collector will not activate if the switch is set to right/left (MNT1/MNT2) position or hostmaintenance mode is on.

 During MNT2, the analog output is fixed at 4.0 mA (or 17.4 mA for oxygen).

NOTE

For the gas alarm contacts and trouble alarm open collector, refer to 7-5 “Operation –Maintenance Mode” of the PS-7-M series gas detector’s instruction manual.

- 54 -

7.5 Full Scale Codes
Full scale information is read in a form of 3-digit full scale code (F.S. code).
Convert the read F.S. code to the corresponding full scale value by referring to the table blow.

F.S. code
010
100
101
102

F.S. value
1
10
100
1000

Full scale code table
F.S. code
F.S. value
030
3
300
30
301
300
302
3000

F.S. code
079
070
700
701
702

F.S. value
0.7
7
70
700
7000

159
150
151
152

1.5
15
150
1500

049
040
400
401
402

0.4
4
40
400
4000

759
750
751
752

7.5
75
750
7500

020
200
201
202

2
20
200
2000

050
500
501
502

5
50
500
5000

089
080
800
801
802

0.8
8
80
800
8000

259
250
251
252

2.5
25
250
2500

069
060
600
601
602

0.6
6
60
600
6000

099
090
900
901
902

0.9
9
90
900
9000

- 55 -

8 Troubleshooting
Before requesting repair, please refer to the table below. If the detector does not return to normal operation
after performing the corresponding steps in the table, or if your issue is not found in the table, consult New
Cosmos or its authorized representative.
Symptom

Cause

ActionModbus TCP(Ethernet)
communicationerror

LAN cable incorrectly
connected
Poor LAN cableconnection

 Check that the status LED 1 islit, which indicates that LAN
cable is correctly connected).
 Connect the LAN cable.
 Check and rewire.
 Turn on all the external devices
that communicate with thisproduct.
 Set the mode change switch to“ETHERNET”.
* Restart the unit after settingwith the DIP switch.
 Check and rewire so that the
number of connected units andtransmission distance arewithin the limit.

Not all devices are on.

Incorrectly set DIP
switch forcommunication mode
The number ofconnected units andtransmission distanceexceed the specified
limit.
Incorrect conditions

Modbus RTU(RS-485)
communication
error

Reference
5.2.2 Modbus TCP(Ethernet) Wiring
Procedure
5.3.2 Status LEDs
5.1 System Configuration

5.3.1 DIP Switches

4.2 Modbus TCP(Ethernet) Communication
Specifications

 Check and reconnect the IP
address, subnet mask, anddefault gateway.
Incorrectly set DIP
 Check that the unit ID (4thswitches for unit ID
value of the IP address) set
with the DIP switches iscorrect.
 Check that the unit ID is not set
to “255”.
* Restart the unit after settingwith the DIP switches.
Same unit ID is used
 Check the IP addresses on thefor more than one unit.
same communication line.
 Check that the unit ID (4thvalue of IP address) is correct.
* Restart the unit after settingwith the DIP switches.
Incorrect wiring
 Check and rewire.
 Securely connect wires toterminals.

6.5 Register Address Map

 Turn on all the external devices
that communicate with thisproduct.
 Set the mode change switch to“RS485”.
* Restart the unit after settingwith the DIP switch.
Check and rewire so that the
number of connected units and

5.1 System Configuration

Not all devices are on

Incorrectly set DIP
switch forcommunication mode
The number ofconnected units and- 56 -

5.3.1 DIP Switches

6.5 Register Address Map
5.3.1 DIP Switches

5.2.1 Modbus RTU(RS-485) Wiring
Procedure

5.3.1 DIP Switches

4.1 Modbus RTU
Communication

SymptomCausetransmission distanceexceed the specified
limit.
Incorrect conditions

Incorrectly set DIP
switches for unit ID

Same unit ID is used
for more than one unit.

Modbus RTU (RS-485)
communication interval
is not good.
No terminal resistors
installed

Received data
incorrect

Communication error
between main unit andbase unit
Poor connection of
main unit

Incorrect function code
Incorrect register
address

Actiontransmission distance arewithin the limit.
 Check that the RS-485 settingof the master and that of thisproduct match, then rewire.
 Check that the unit ID set with
the DIP switches is correct.
 Check that the unit ID is not set
to “255”.
* Restart the unit after settingwith the DIP switches.
 Check the unit IDs on the samecommunication line.
 Check that the unit ID iscorrect.
* Restart the unit after settingwith the DIP switches.
Check
the Modbus RTU
protocol communicationinterval, then rewire.
 Check that the terminal
resistors are used at both endsof the communication line.
Install them if they are notinstalled.
 Set the terminal resistor switch
to the on position.
 Check that the status LED-3
flashes, which indicates thatthe communication status
between main and base units isnormal.
If lit, it means that there is no
response from main unit, and if
not lit, it means that there is norequest from base unit.
 Remove and reinstall the mainunit.
 Check that the function code iscorrect.
 Check the register addresses
specified are correct.

- 57 -

ReferenceSpecifications

4.1 Modbus RTU
Communication
Specifications
5.3.1 DIP Switches

6.5 Register Address Map
5.3.1 DIP Switches

6.1.4 Modbus RTU
Communication Interval
5.1 System Configuration

5.3.2 Status LEDs

6.2 Function Codes
6.5 Register Address Map

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Osaka 532-0036, Japan
https://www.newcosmos-global.com