Modbus Tcp - Algodue ELETTRONICA UPM309 Manual Del Usuario

2.2 MODBUS TCP

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 TCP.
READING COMMAND STRUCTURE
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
Transaction ID
Protocol ID
Data bytes
Unit ID
Function code
Starting register
Words to be read
Query example: 010000000006010300000002
Structure
Transaction ID
Protocol ID
Data bytes
Unit ID
Function code
Reading bytes
Requested reading data
Response example: 01000000000701030400039210
56
Example Byte
01 -
00 High
00 Low
00
High
00 Low
06 -
01 -
03 -
00 High
00 Low
00 High
02 Low
Example Byte
01 -
00 High
00 Low
00 High
00 Low
07
-
01 -
03 -
04 -
00 High
03
Low
92 High
10 Low
MODBUS RTU/ASCII, TCP