Modbus Master serial diagnostic counters - Grid automation - Communication Protocol Manual - REC615 Grid Automation - PCL1 - IEC - ANSI

REC615 Modbus Master Communication Protocol Manual

Modbus Master serial diagnostic counters can be viewed via the HMI path Monitoring > Communication > Protocols > Modbus Master (n).

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.

Table 1. Modbus Master Serial diagnostic counters
Counter Description
Status

"True" if the serial instance is in use and at least one Modbus slave is connected and its reply messages are received within the set intervals.

"False" otherwise
Reset counters

True = Reset all diagnostic counters

False = all diagnostic counters values are kept
Received frames

Total amount of received frames.
Transmitted frames

Total amount of transmitted frames.
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.
Transmitted exc A

Incremented when:

  • Polling synchronization is lost, e.g. the wrong slave unit replies to the polling message
  • An exception response is received
  • The slave unit replies with an unexpected function code
  • The wrong amount of data received doesn’t match the expected
  • The data received saturates the limits of the signal to which is mapped to
Transmitted exc B

Incremented when:

  • Data polled from the slave(s) couldn’t be updated into the mapped signals
Connection errors

Total amount of times a poll request to a slave was not replied to or acknowledged.