Liquistation CSF22 MODBUS
®
-Guideline
Hauser
© Copyright Dez. 2011
7
3.
Function description
3.1.
Communication module 485
The measuring device is an assembly of modules, which are connected to a backplane residing inside a casing. For
using Modbus communication a
485
module has to be present with appropriate licensing.
3.2.
Modbus function codes
Liquistation supports the following Modbus function codes:
Function
code FCxx
Name
Description
03
READ HOLDING REGISTER
Reading one or several register of the Modbus slave
1 to max. 125 successional register can be read (1 register = 2
bytes) with one telegram.
Usage:
This function code is used to read register with read/write
access.
04
READ INPUT REGISTER
Reading one or several register of the Modbus slave
1 to max. 125 successional register can be read (1 register = 2
bytes) with one telegram.
Usage:
This function code is used to read register with read access.
08
DIAGNOSTICS
This function code is used to check the communication
between Master and Slave.
The following sub function codes are supported:
• Sub
-function 00 = Return Query Data (Loopback test)
•
Sub-function 02 = Return Diagnostics Register
16
WRITE MULTIPLE REGISTERS
This function code is used to write several registers with a
single request. Up to 123 successional registers can be written.
All parameters addressed by the written registers need to be
writable, otherwise the query is answered with an exception
ILLEGAL DATA VALUE.
23
READ/WRITE
MULTIPLE REGISTERS
This function code is used to write several registers and read
several registers with one single Modbus transaction. Up to
118 successional registers can be read and written. The write
operation is executed before the read
Hint:
•
Broadcast messages are possible only with function codes 06, 16 and 23.
