OPERATION IN THE MODBUS TCP NETWORK – SERVER MODE
6 OPERATION IN THE MODBUS TCP NETWORK – SERVER MODE
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NOTE!
The RS485, USB and Ethernet interfaces, for using the same functions to access the data and
programming of the equipment, must not be used simultaneously to perform program download
or on-line monitoring functions of the SSW900 soft-starter, because conflicts may occur during the
simultaneous access to the data.
6.1 AVAILABLE FUNCTIONS
In the Modbus specification are defined the functions used to access different types of data. In the SSW900, in order
to access those data the following services (or functions) have been made available:
Table 6.1:
Supported Modbus Functions
Code
Name
Description
03
Read Holding Registers
Reading of register blocks of the holding register type.
06
Write Single Register
Writing in a single register of the holding type.
16
Write Multiple Registers
Writing in register blocks of the holding register type.
22
Mask Write Register
Writing in holding register using mask.
23
Read/Write Multiple registers
Reading and writing in register blocks of the holding regis-
ter type.
43
Read Device Identification
Identification of the device model.
6.2 MEMORY MAP
The soft-starter SSW900 has different types of data accessible through the Modbus communication. These data are
mapped at data addresses and access functions as described in the following items.
6.2.1 Parameters
The SSW900 soft-starter Modbus communication is based on the reading/writing of the equipment parameters. All
parameters of the equipment are available as 16-bit holding registers. The data addressing is done with the offset
equal to zero, which means that the parameter’s network address (Net Id) corresponds to the register address.
It is necessary to know the device list of parameters to be able to operate the equipment. Thus, it is possible to
identify what data are needed for the status monitoring and the control of the functions. The main parameters are:
Monitoring (reading):
S5.1.1 (holding register address 680): Status Word SSW
Command (writing):
Refer to Appendix A for a complete parameter list of the equipment.
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