DS 400 Side 12 of 36
7 Modbus addressing model
The DS400 RS485 Modbus allows read/write access according chapter 8
Not defined registers are not accessible / not supported.
Byte Order:
The size of each Modbus-register is 2 Byte. For a 32 bit value two Modbusregister will be read out by
the DS400. Accordingly for a 16bit Value only one register is read.
Ausgabeformat DS400:
Single Word Double Word
For verification of a correct dataformat please read out register 64000 or 64004.
Result should be.
Register 64000: Long Integer Value =1 000 000
Register 64004: Float Value = 1 000 000
7.1 Function Code 3 (Read holding register)
General exceptions:
• Requesting less than 1 or more than 125 registers => Exception 3 (Illegal data value)
• Requesting more than max. message size (27 registers) => Exception 2(Illegal data address)
• Requesting data out of defined range of registers chapter 8 => Exception 2 (Illegal data address)
Application exceptions:
• Application errors => Exception 4 (Slave device error)
Holes/register alignment:
• The read command always returns data if no exception is given. Bad
Start/end alignment will result in only parts of the data item being read.
HByte LByte
18 => 00 12
Data Order 1. Byte 2. Byte
12 00
HWord LWord
HByte LByte HByte LByte
29235175522 => AE 41 56 52
Data Order 1.Byte 2.Byte 3.byte 4.Byte
56 52 AE 41
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