4–24 869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUALDEVICE CHAPTER 4: SETPOINTSMODBUS SLAVE ADDRESSRange: 1 to 254 in steps of 1Default: 254For the RS485 ports each 869 must have a unique address from 1 to 254. Address 0 isthe broadcast address to which all Modbus slave devices listen. Addresses do not haveto be sequential, but no two devices can have the same address, otherwise conflictsresulting in errors occur. Generally, each device added to the link uses the next higheraddress starting at 1.MODBUS TCP PORT NUMBERRange: 1 to 65535 in steps of 1Default: 502The TCP port number used with Modbus over Ethernet. Note that the maximum numberof simultaneous Modbus connections supported over Ethernet is:• three for an 869 without the communications card,• five for an 869 with the communications card.COMPATIBILITYRange: Disabled, SR469Default: DisabledThe Compatibility mode changes the Modbus actual value registers to emulate theSR469. The emulation supports typical actual value data for common data items. Seethe 8 Series Protective Relay Communications guide for the list.NOTENOTE:When the device is programmed as a SR469, 869 actual values cannot be retrieved fromModbus.MODBUS ACTIVITY TIMEOUTRange: 0 to 3600 s in steps of 1Default: 0 sThe Modbus Activity Timeout specifies the minimum time without Modbuscommunication. This timeout is used to declare the Modbus ‘Loss of Communication’state.The Modbus state is always Active if the Modbus Activity Timeout is 0 s.MODBUS ERROR RESPONSESThe following exception response codes are implemented.Function Code 03H (Read Setpoints)Modbus Implementation: Read Holding Registers869 Implementation: Read SetpointsFor the 869 implementation of Modbus, the function code can be used to read anysetpoints (“holding registers”). Holding registers are 16 bit (two byte) values transmittedhigh order byte first. As a result all 869 Setpoints are sent as two bytes. The maximumnumber of registers that can be read in one transmission is 125.Error ID Exception Description01 ILLEGAL FUNCTION The function code transmitted is not one of thefunctions supported by the 869.02 ILLEGAL DATA ADDRESS The address referenced in the data field transmittedby the master is not an allowable address for the 869.03 ILLEGAL DATA VALUE The value referenced in the data field transmitted bythe master is not within range for the selected dataaddress.
