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REX640 Modbus Communication Protocol Manual

Modbus TCP/IP counters can be viewed via the HMI path Monitoring > Communication > Protocols > Modbus (n).

The counters show the complete Modbus protocol link frames and Modbus errors. The Ethernet communication driver maintains its own counters for lower level communication diagnostics.

Table 1. TCP/IP diagnostic counters
Counter Description
Status Shows the value "True" if the TCP/IP or serial instance is in use. This means that a Modbus client has connected to the TCP socket and Modbus TCP messages are received regularly at least at 15-second intervals or faster. In all other cases this value shows "False".
Reset counters True = Reset all diagnostic counters
Received frames Total amount of received Modbus frames.
Transmitted frames Total amount of transmitted Modbus responses.
Transmitted exc A Total amount of exception responses 1 and 2. These exception responses usually reveal configuration errors on the Modbus client’s side.
Transmitted exc B Total amount of exception responses 3. These exceptions reveal the protection relay application level rejections.
Table 2. Common (instance independent) Modbus TCP/IP diagnostic counters
Counter Description
CnReject no sockets The amount of connection requests that are rejected due to unavailable TCP sockets.
CnReject unregistered The amount of connection requests that are rejected since the client is not registered.