Danfoss VLT FC 360 Design Manual

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Danfoss VLT FC 360 Design Manual Manual pdf 49 page image

NOTE4-14 Motor Speed High Limit [Hz] is a single word, and theparameter command for write in EEPROM is “E”. Parameter4-14 is 19E in hexadecimal.The response from the slave to the master is:119E HPKE IND PWE high PWE low0000 H 0000 H 03E8 H130BA093.10Illustration 3.9 Response from Master3.5.2 Reading a Parameter ValueRead the value in 3-41 Ramp 1 Ramp up TimePKE=1155 Hex - Read parameter value in 3-41 Ramp 1Ramp up TimeIND=0000 HexPWEHIGH=0000 HexPWELOW=0000 Hex1155 HPKE IND PWE high PWE low0000 H 0000 H 0000 H130BA094.10Illustration 3.10 TelegramIf the value in 3-41 Ramp 1 Ramp up Time is 10 s, theresponse from the slave to the master is:130BA267.101155 HPKE IND0000 H 0000 H 03E8 HPWE high PWE lowIllustration 3.11 Response3E8 Hex corresponds to 1000 decimal. The conversionindex for 3-41 Ramp 1 Ramp up Time is -2, that is, 0.01.3-41 Ramp 1 Ramp up Time is of the type Unsigned 32.3.6 Modbus RTU Overview3.6.1 AssumptionsDanfoss assumes that the installed controller supports theinterfaces in this document, and strictly observe allrequirements and limitations stipulated in the controllerand frequency converter.3.6.2 What the User Should Already KnowThe Modbus RTU (Remote Terminal Unit) is designed tocommunicate with any controller that supports theinterfaces defined in this document. It is assumed that theuser has full knowledge of the capabilities and limitationsof the controller.3.6.3 Modbus RTU OverviewRegardless of the type of physical communicationnetworks, the Modbus RTU Overview describes the processa controller uses to request access to another device. Thisprocess includes how the Modbus RTU responds torequests from another device, and how errors are detectedand reported. It also establishes a common format for thelayout and contents of message fields.During communications over a Modbus RTU network, theprotocol determines:• How each controller learns its device address• Recognizes a message addressed to it• Determines which actions to take• Extracts any data or other information containedin the messageIf a reply is required, the controller constructs the replymessage and sends it.Controllers communicate using a master-slave technique inwhich only one device (the master) can initiatetransactions (called queries). The other devices (slaves)respond by supplying the requested data to the master, orby taking the action requested in the query.The master can address individual slaves, or can initiate abroadcast message to all slaves. Slaves return a message(called a response) to queries that are addressed to themindividually. No responses are returned to broadcastqueries from the master. The Modbus RTU protocolestablishes the format for the master’s query by placinginto it the device (or broadcast) address, a function codedefining the requested action, any data to be sent, and anerror-checking field. The slave’s response message is alsoconstructed using Modbus protocol. It contains fieldsconfirming the action taken, any data to be returned, andan error-checking field. If an error occurs in receipt of themessage, or if the slave is unable to perform the requestedaction, the slave constructs an error message, and send itin response, or a time-out occurs.RS-485 Installation and Set... VLT® AutomationDrive FC 360 Design GuideMG06B202 - VLT® is a registered Danfoss trademark 473 3