Program features 45
Modbus/TCP gateway
The NETA-21 supports a subset of the Modbus/TCP protocol specification v1.1b. This
allows to use a normal TCP/IP connection to access the parameters of drives.
The supported functions are:
• 03 (0x03) Read Holding Registers
• 06 (0x06) Write Single Register
• 16 (0x10) Write Multiple registers
• 23 (0x17) Read/Write Multiple registers
• 43 (0x2B) Encapsulated Interface Transport
To enable the service for selected network interfaces (by unlocking it in the NETA-21
internal firewall), go to Settings –> Network services –> Services.
With a normal PC and a program that supports the Modbus/TCP protocol in the same
network to which the NETA-21 is connected, you can query values of parameters from the
connected devices. The Modbus/TCP client configuration requires you only to specify the
IP of the NETA-21 and port 502.
The Modbus protocol supports up to 247 devices. Each device is identified with an ID, a
number from 1 to 247.
The ID used by a specific device can be determined with its internal name (shown in the
Modbus/TCP gateway panel under Device interfaces). This name always ends with a
number that represents the index inside the range of the IDs of the specific protocol. For
example, a slave device connected through the Modbus/RTU protocol with station address
3 (device node ID mb_3) is accessible by Modbus/TCP gateway station address 99 (97+3-
1).
To access a specific parameter of a given group and index, you must specify an address
by calculating it according to one of the following formulas:
16-bit address = (4)0000 + 100 × group + index
ID range Protocol
1…32 fiber optics
33…64 Panel bus 1 (port PNL1)
65…96 Panel bus 2 (port PNL2)
97…128 Modbus/RTU
129…160 Ethernet tool network
161…247 Reserved
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