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2 sensor administration under modbus, Sensor administration under modbus -6 – YSI DIQ/S 182-MOD System 182 User Manual

Page 118

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Modbus connection

System 182

7 - 6

ba76025e01

02/2012

Query and response

telegram

Data transmission takes place via query and response telegrams. The
form of the telegrams is determined by the Modbus RTU protocol. The
Modbus master transmits a query telegram with a Modbus command to
the Modbus slave (here, the DIQ/S 182-MOD). The Modbus slave
transmits a response telegram with the requested data from the sensor
data block or an error message.

Supported

Modbus commands

The DIQ/S 182-MOD provides the data block for read access only.
Writing Modbus commands are not carried out.

7.4.2

Sensor administration under Modbus

Preparation of the IQ S

ENSOR

N

ET

for communication with the Modbus

may require, e.g. the following:

 Creating an IQ S

ENSOR

N

ET

system with specific assignment of

sensor numbers to sensors

 Creating several IQ S

ENSOR

N

ET

systems with the identical

assignment of sensor numbers to sensors

 Changing the order of the sensors in an already installed system

Creating the assignment

of sensor numbers

You want to install an IQ S

ENSOR

N

ET

system and, at the same time,

create a specific sequence of sensor number assignments to the
sensors.

Modbus commands

Command code

Read Input Register

04h

Read Discrete Inputs

02h

Read Holding Register

03h

Read Coils

01h

1

Carry out a system start without any sensors (see section
3.10).

2

Connect the sensors to the system in the required order. With
each sensor wait until the system has recognized the sensor.