Command Structure - Chauvin Arnoux ULYS FLEX Modbus Notice De Fonctionnement

2. COMMAND STRUCTURE

The master communication device can send reading or writing commands to the slave (instrument). In this
section, the tables describe the reading command structure (Query) and the writing command structure. Both
commands are followed by a response sent by slave.
These tables refer to a master-slave communication in MODBUS RTU.
READING COMMAND STRUCTURE (function code $03/$04)
The master communication device can send commands to the instrument to read its status, setup and the
measured values. More registers can be read, at the same time, sending a single command, only if the registers
are consecutive (see chapter 4). Values contained both in Query and Response messages are in hex format.
Structure
Slave address
Function code
Starting register
Words to be read
CRC
Query example: 0103000000020BC4
Structure
Slave address
Function code
Data bytes
Requested reading data
CRC
Response example: 010304000392109F66
44
Example Byte
01 -
03 -
00
High
00 Low
00 High
02 Low
0B High
C4 Low
Example Byte
01 -
03 -
04 -
00 High
03 Low
92 High
10 Low
9F High
66
Low
MODBUS RTU/ASCII