Application Examples; Examples Of Modbus Communication - Siemens SENTRON PAC RS485 Manual

Application examples

12.1

Examples of MODBUS communication

General information
The master makes a request to the slave, the SENTRON PAC Power Monitoring Device.
This replies to the master and confirms that it has executed the request.
Below is a representation of communication between the master and the slave using some
application examples from the "Application Log-File" of the bus master. The values are
specified in hexadecimal form.
Read measured values
Table 12-1 Request of the master
Address FC
01 04
Explanation:
Table 12-2 Response - confirmation of the slave
Address FC
01 04
Explanation:
PAC RS485
Manual, 02/2008, A5E02091800B-01
From register
00 01
From offset 0001:
voltage Va-n
Number of read bytes
0C
12
Number of registers to be read
00 06
Bytes
43 68 70 22
43 67 60 DC
43 67 9C A5
232.4
231.4
231.6
12
CRC
21 C8
CRC
41 D7
75