Vaisala Indigo500 Series, Руководство пользователя

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8. Modbus
8.1 Modbus overview
Indigo500 transmitters support the Modbus TCP/IP communication protocol (over Ethernet).
The transmitter and the connected probes are treated as separate Modbus slaves, each with
their own fixed unit identifier (unit ID) value.
Note the following limitations of the Modbus implementation:
• Use only one Modbus TCP/IP connection at a time. Design the system so that only one
Modbus TCP/IP client accesses the transmitter.
• Modbus TCP/IP can process reliably only one Modbus transaction at a time. Reduce the
polling rate of the client to avoid nested transactions.
The transmitter's Modbus response time is approximately 2000 ms. If the Modbus client gives
a timeout error, increase the request timeout parameter.
The transmitter's Modbus server port is 502.
More information
‣ Enabling Modbus TCP/IP on touchscreen (page 83)
‣ Enabling Modbus TCP/IP in web interface (page 92)
8.2 Unit identification of transmitter and probes
The transmitter and the connected probes are treated as separate Modbus slaves, each with
their own fixed unit identifier (unit ID) value. The unit ID in the Modbus request defines the
intended recipient of the request (transmitter or probe).
Table 13 Unit IDs of transmitter and probes
Device Unit ID
Transmitter with barometer module 240
Probe connected to probe 1 connection terminal 241
Probe connected to probe 2 connection terminal 242
The unit IDs of the connected probes identify the probes based on the probe connection
terminal that they are connected to. The probes use these unit IDs (241 and 242) only when
they are connected to the transmitter. When the probes are accessed directly without the
transmitter, the probes have their own Modbus address settings instead of these unit IDs.
If the probe fails to respond to the request, the transmitter responds to the client with the
exception code
Gateway Target Device Failed to Respond
.
Indigo510, Indigo520 User Guide M212287EN-N
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