DEEP SEA ELECTRONICS PLC - Home Mega Global Solution

DSE 5xxx Configuration Software Manual7.3.1 TYPICAL BUILDING MANAGEMENT SCHEME USING RS485 MONITORINGCAUTION!:- . RS485 cabling must be 120impedance cable, specified for use withRS485. 120 terminating resistors must be fitted to the first and last devices on thebus. Some PC RS485 cards are already fitted with this resistor, and in this case shouldnot be fitted externally. If in doubt, consult the supplier of your PC RS485 card.If the 52xx/53xx controler is the ‘last’ device on the bus, then it’s RS485 connectionmust be suitably terminated with a 120 resistor as detailed in the specification laidout in the RS485 standard.Recommended cable BELDEN 9841 120RS485 cable.DSE part number 016-030.NOTE:- The RS485 output uses ‘MODBUS’ protocol. It is possible to use thirdparty software to monitor and control the 52xx/53xx module via this protocol.Please refer to Deep Sea Electronics Plc for details.7.3.2 MODBUSThe RS485 output usesModbus communications protocol. This uses a master-slave techniqueto communicate. Only the Master can initiate a packet transaction, caled a ‘query’. Whenappropriate the slave (52xx/53xx Module) responds to the query and provides the informationrequested by the master.All supported data can be read and written as specified in the register table (documentation isavailable from Deep Sea Electronics Plc.).When the 52xx/53xx Module receives a query it will respond by either supplying the requestedregister data or performing the requested action. A slave device (the 52xx/53xx module) willnever initiate communications on theModbus link. The 52xx/53xx can only be configured as aslave device. The Master can only query individual slaves. Refer to theModbus protocoldocument for more details.DSE5xxx Configuration software ISSUE 2 02/07/04 AM 87