MIQ/2-MOD
Interface for the Modbus RTU
17
ba75973e01
07/2012
Sensor data block
The datasets of the sensors are made available to the Modbus master
in a sensor datablock in the IQ S
ENSOR
N
ET
.
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 com
-
mand to the Modbus slave (here, the IQ S
ENSOR
N
ET
). The Modbus
slave transmits a response telegram with the requested data from the
sensor data block or an error message.
Supported
Modbus commands
The IQ S
ENSOR
N
ET
provides the data block for read access only. Writ
-
ing Modbus commands are not carried out.
3.5.2 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 sen
-
sor numbers to sensors
Creating several IQ S
ENSOR
N
ET
systems with the identical assign
-
ment of sensor numbers to sensors
Changing the order of the sensors in an already installed system
The transmitted data of all IQ S
ENSOR
N
ET
sensors is given
in the WTW document, "IQ S
ENSOR
N
ET
sensors: encoded
data for field bus communication" (ba75560de). It is regu
-
larly updated when new sensors are introduced and when
the sensor software is changed (if it concerns the transmit
-
ted sensor data). The latest version is available on the
Internet, in the download area for operating manuals.Use
the search function for the download and search for
"ba75560de".
Check the transmitted data for agreement of the requested
and transmitted sensor number (Sxx) before any further
processing.
Modbus commands
Command code
Read Input Register
04h
Read Discrete Inputs
02h
Read Holding Register
03h
Read Coils
01h