Danfoss VLT 5000 Operating Instructions Manual

Also see for VLT 5000: Manual Operating instructions Operating instructions Instruction manual Operating instructions

Danfoss VLT 5000 Operating Instructions Manual Manual pdf 4 page image

VLT ® 5000/ 5000 FLUX/ 6000 HVAC/8000 AQUA DeviceNetIntroduction toDanfoss VLT seriesand DeviceNetPhase 2:Is the interface watchdog function performed bythe option card as the first operational action. Aftercompletion of this phase, data can be passed betweenthe VLT frequency converter and the option cardthrough the command channel in the dual port RAM.Phase 3:The VLT frequency converter will write to the InitializationChannel of the dual port RAM which will set thedisplacement values of the various channels (ControlChannel, Status Channel, Command Channel 1,Command Channel 2, Command Channel 3, WarningChannel, and Spontan Channel), and the DeviceNetoption card software will read these displacementsand return a response to the VLT frequency converternotifying that the initialization was successful or anerror was obtained in the process.During operation (after initialization) the dual port RAMinterface is supervised by a watch-dog in the VLTfrequency converter. The VLT frequency converter willbe kept "alive" by cyclic writing to a channel in the dualport RAM by the watch-dog handler of the option card. Network Variable HandlingThe parameter access network variable is a structurecontaining parameter number, data, value, and afunction code containing a read or write command.The application program shall receive the data,validate the data, convert the data to the format ofthe VLT frequency converter, process the read orwrite of the parameter, then send the informationback in an output network variable of the samestructure. This output variable would contain theparameter number, error code information in the eventof an exception, and parameter value. Error HandlingThe option card will stop sending a watchdog signalto the VLT frequency converter when:1. The node has been disconnected from the network2. A network management tool has theOption Card go Off-line3. A hardware fault on the DeviceNet Option CardPCB prevents reliable operationBy withholding the watchdog message, the VLTfrequency converter can detect a "Bus Time-out"and enter secure, pre-defined state.For recoverable errors such as [1] and [2] the optioncard shall re-send the watchdog message whenthe fault or condition has disappeared such as afterre-connection of the node to the network.For unrecoverable errors such as [3] the applicationprogram shall permit logging of network errorswithout resetting or restarting the microprocessor.This will send information to a network managementtool that will allow appropriate actions to be taken.The only way to recover from a serious error is tore-initialize the VLT frequency converter DeviceNetoption card by cycling power.In case of serious VLT frequency converter fault, theDeviceNet processor shall hold the CAN chip reset,thereby disabling any communication to the node untilthe VLT frequency converter has been re-initialized. Overall FunctionDeviceNet is a low-level network that standardizescommunications between industrial devices (sensors,limit switches) and high level devices (controllers).The communication network can be peer to peer ormaster/slave. DeviceNet uses CAN technology forMedia Access Control and Physical Signaling and itsupports up to 64 nodes. DeviceNet also definesdevice profiles for devices belonging to specific classes.For other devices, a custom class must be defined inorder to make it DeviceNet compatible. This furtherenhances the interchangeability and interoperability ofthe network. Each node on the network has its ownunique media access control identifier (MAC ID) todistinguish it on the network. The MAC ID is storedin the header of the message which is split into fourdifferent message groups. However, DeviceNet onlymakes use of three message groups keeping the fourthone for future use. If two nodes attempt to get controlof the network bus simultaneously, the CAN protocolresolves the issue by arbitration. A dominant bit (0)will win arbitration over a recessive bit (1).For the VLT frequency converter, the option cardwill be slave node on the DeviceNet network. Theoption card will be a message server that will requestand set parameters in the VLT via a dual portedRAM interface. The option card has an embeddedCAN controller that will screen all network messageswith a Mask and Match register. This featureallows the option card to filter out any unwantedmessages from the network. The option card willreceive group 2 and group 3 messages. Group 2messages allows the option card to use the predefinedMaster/Slave connection set which identifies a usefor all group 2 message identifiers. The ability toMG.50.H4.02 - VLT is a registered Danfoss trademark 3