Modbus serial diagnostic counters can be viewed via the HMI path .
The counters show complete Modbus protocol link frames and Modbus errors. The serial communication drivers (COM1, COM2) maintain their own counters for lower level serial communication diagnostics.
| Counter | Description |
|---|---|
| Status |
Shows the value "True" if the serial instance is in use. This indicates that the Modbus client is connected and Modbus messages, which are addressed to the device, are received regularly at least with a 15 second interval or faster. In all other cases this value is "False". |
| Reset counters | True = Reset all diagnostic counters |
| Received frames | Total amount of received Modbus frames. For example, the Modbus frames that are addressed to this instance. |
| 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 side. Either the client uses a request function code which is not supported or the requested Modbus point(s) does not exist. |
| Transmitted exc B | Total amount of exception responses 3. These exceptions usually reveal the protection relay application level rejections. That is, the protection relay application rejects the request at this moment, under the current circumstances. The exception can also mean that the value in the Modbus write request is out of range. |
| Checksum errors | Total amount of detected Modbus checksum errors. The Modbus instance only calculates checksums of Modbus frames that contain a proper link address. All other incoming Modbus frames are discarded. |