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Model BB4000 Controller Instruction Manual
19.2. 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.
19.3. 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 Parameters 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
Parameters 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 Function and not send out a Response.
19.4. 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.