General; Modbus Setup; Function Code / Exception Code - YOKOGAWA DO71 Manual

1. General

Optical Dissolved Oxygen sensors are slave devices which can be configured or are sending
process data using Bi-directional digital communication (RS485, half-duplex) with full MODBUS
(RTU) support. The power for the Optical Dissolved Oxygen sensors must be supplied by a HOST
or by a separate power supply in the range +7VDC up to +30VDC. Maximum power of the Optical
Dissolved Oxygen sensors is 1W in active mode, and 150mW in stand-by mode.

1.1 MODBUS setup

The following list shows the required setting by HOST to establish communication between the
HOST as master device and the Optical Dissolved Oxygen sensor as slave device. The procedure
for changing list items is explained in the following chapters in this document.
Slave address
Serial Profile
NOTE
Slave address and Serial Profile are configurable as explained in this document.
In case of using multiple Optical Dissolved Oxygen sensors in a bus system, connected to one HOST,
the Slave addresses of all the Optical Dissolved Oxygen sensors must be unique. Because initial
setting of address is 1 it is recommended to change the initial address value to prevent communication
conflicts in case a new purchased Optical Dissolved Oxygen sensor is added to the bus.
Serial profile of the slave device(s) must be the same as the HOST.

1.2 Function code / Exception code

MODBUS Function codes used for DO71 and DO72:
Function
Read Hold Register
Write Single Register
Write Multiple Registers
Exception codes used for DO71 and DO72:
Name
Illegal Function
Illegal Data Address
All Rights Reserved. Copyright © 2022, Yokogawa Process Analyzers Europe B.V.
MODBUS Communication – General
: 1
: 19200 bps, 8 data bits, No parity, 2 stop bits
Function code (hex)
03
06
10
Meaning
Exception code
The Function code received is not an
0x01
allowable action for the slave
The Data Address received is not an
0x02
allowable address for the slave
5
TI 12J06J01-00EN-P