Supported Function Codes - BONFIGLIOLI Vectron Agile Communications Manual

7.3

Supported Function Codes

Modbus definitions for reading/writing data in a device do not fit directly to parameter access of inver-
ters (independent of inverter manufacturer). Modbus is defined for reading/writing bits and registers
in a different way. Furthermore, data access is limited to 16 bit wide data.
To fulfill the Modbus requirements the data access to parameters in the devices (inverters) will use
the following defined function codes:
16 bits values:
− Function Code 3, Read ONE 16 bit wide data (Read Holding Register)
(Preset Single Register)
− Function Code 6, Write ONE 16 bit wide data
(Preset Multiple Register)
− Function Code 16, Write ONE 16 bit wide data
−
32 bits values:
For data access to 32 bit wide data two new inverter specific function codes are defined:
(Read Holding Register)
− Function Code 3, Read two 16 bit (=32 Bit) wide data
− Function Code 16, Write two 16 bit (=32 Bit) wide data (Preset Multiple Register)
− Function Code 100, Read ONE 32 bit wide data
− Function Code 101, Read ONE 32 bit wide data
Note: The Modbus specification doesn't specify the handling of 32 bit values. The implemented han-
dlings and function codes to access 32 Bit values are however widely spread and commonly used.
These functions allow data access to 32-bit "long" variables/parameters in the inverter.
Diagnostics
For diagnostic purposes the Modbus function code "8" ( ) is also supported.
These function codes and their corresponding data fields are described in detail in the following chap-
ters.
Note:
In all data fields with more than one byte, the highest order byte is transmitted first.
Message examples for all supported function codes in both RTU and ASCII transmission modes can be
found in Chapter 9 "Modbus Message Examples".
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