Data exchanges take place in one of two modes:
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server mode: The RTU module supports all Modbus-over-TCP requests from the .
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client mode: This type of exchange enables Modbus-over-TCP requests to be sent using the functions:
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READ_VAR
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WRITE_VAR
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DATA_EXCH
NOTE: The maximum Ethernet frame size depends on the type of transaction. The maximum frame size is 256 bytes for messaging.
The BMENOR2200H module manages these TCP connections through messaging:
TCP/IP reserves specific server ports for specific applications through IANA (Internet Assigned Numbers Authority). Modbus requests are sent to registered software port 502.
Port 502 messaging paths:
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server path:
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Port 502 messaging can process up to 8 incoming requests from the network. Requests are received during the previous scan and sent to the Modbus server in the IN section.
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Port 502 messaging can process up to 8 responses from the Modbus server in the IN section (including writing the data into the socket).
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client path:
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Port 502 messaging can process up to 16 outgoing requests from the application in the OUT section (including writing the data into the socket).
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Port 502 messaging can process up to 16 incoming responses from the network in the IN section. Responses are sent to the application.
