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SCADA TROUBLESHOOTING
Communication Activity Indicator
The Communication Activity Indicator (Parameter d.07) may be used to help troubleshoot communication issues.
It typically pulses from “0” to “1” momentarily to indicate that the master is sending a message. It may stay “1” if there is
very little time between messages.
It does not indicate that a valid communication has occurred, only that there is activity on either the RS232 port or the
Ethernet port.
When using the Ethernet Port, the Ethernet Board logic will block messages with the wrong IP Address, or when there
are setup issues with the Ethernet Port. For the Activity Indicator to be pulsed, the message must be accepted and
passed through the Ethernet Board to the Main Controller Board.
Address of Last Slave Polled by Master
The Address of Last Slave Polled by Master (Parameter d.08) may be used to help troubleshoot communication issues.
When using the RS232 port, it shows the address of the last slave that was polled by the master.
When using the Ethernet Port, the Ethernet Board logic will block messages with the wrong IP Address, or when there
are setup issues with the Ethernet Port. For Parameter d.08 to show the slave address, the message must be accepted
and passed through the Ethernet Board to the Main Controller Board.
Record of Last Modbus Message
If the Slave Address is acceptable and the message does not have an Overrun Error (FLC = 1), Time Out Error (FLC =
2), Framing Error (FLC = 13), or Noise Error (FLC = 14) then the entire Modbus message will be present in data Pa-
rameters d.08 - d.86. If the Slave Address is not acceptable or if any of these errors are encountered, the rest of the
message is rejected and does not show up in Parameters d.08 - d.86. If the entire message is received (present at Pa-
rameters d.08 - d.86), it may fail the Checksum Test (FLC = 4), have an Invalid Modbus Function Code (FLC = 5), or
have one of 7 other faults (FLC = 6, 7, or 31 - 35). Failing any of these tests will cause the logic to not perform the Func-
tion and not send out a Response.
Communication Fault Codes
Communication Faults will often generate a Fault Code (Parameters FLC and LFC) that may be used to help determine
the cause of a communication problem. When this occurs the Fault Indicator will come on.
A valid communication after a Fault will zero Parameter FLC, and will make the Fault Indicator turn off, but the Fault
Code will still be available at Parameter LFC. See the Fault Code Table for the description of the communication Fault
Codes 1 - 7, 13 - 14, 31 - 35, and 37.
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