Eaton PowerXL DE1 Manual

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Contents

7 Modbus RTU7.4 Operating mode Modbus RTUDE1 variable speed starter 09/14 MN040011EN www.eaton.com 1197.4.1 Structure of a master request7.4.1.1 Address• Parameter P-34 is used to enter the address (1 up to 63) of the variablespeed starter to which the request will be sent. Only the variable speedstarter with that address will be able to respond to the request.• Address 0 is used as a so-called Broadcast (message to all bus users)from the master. In this mode, individual modules cannot be addressedand data cannot be output from the slaves.7.4.1.2 Function codeThe function code defines the type of message.The following actions can be performed with DE1 variable speed starter:7.4.1.3 DataThe length of the data block (data: N x 1 bytes) depends on the functioncode. The function code is made up of two hexadecimal values and has arange of 00 to FF. The data block contains additional information for the slavethat will enable the latter to perform the operation specified by the master inthe function code (this information may specify the parameters that need tobe processed, for example).7.4.1.4 Cyclic redundancy check (CRC)Frames in the Modbus RTU operating mode include a cyclic redundancycheck (CRC). The CRC field is made up of two bytes that contain a binary16-bit value. The CRC check is always run independently of the parity checkfor the individual characters of the telegram. The CRC result is appended tothe frame by the master. While receiving the frame, the slave performs anew calculation and compares the calculated value to the actual value in theCRC field. If both values are not identical, an error is set.Function code [hex] Designation Description03 Read Holding Registers Reading of the holding registers in the slave (processdata, parameters, configuration).A master request enables up to 11 registers to be read.06 Write Single Register Writing of a holding register in the slave.With a general telegram (Broadcast) the appropriateholding registers are written in all slaves. The registeris read back for comparison.