Delta DPM-D520I, User Manual

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Chapter 5 Parameters and Functions
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5.2 Modbus Protocol
5.2.1 Supported Modbus Function Code
Function Code Modbus Name Content
0x03 Read Holding Registers Read the contents of read location
0x06 Preset Single Registers Preset the contents of written location
0x10 Preset Multiple Registers Preset the contents of written locations
0xFE Read Data Log/THD/alarm Log Read the contents of data
log/THD/alarm log
When the protocol is Modbus RTU, the maximum address to be gathered with a single Modbus block read is
125 for function code 0x03, and the maximum address is 123 for function code 0x10. When the protocol is
Modbus ASCII, the maximum address to be gathered with a single Modbus block read is 60 for function code
0x03, and the maximum address is 59 for function code 0x10.
Function code
0xFE
is only supported when the protocol is Modbus RTU.
5.2.2
Modbus Communication Protocol
With Modbus RTU, Modbus master sends the Request message which contains Function code 0x03- request
Slave to answer values corresponding to the Modbus address. Modbus Slave in response sends the requested
data. Modbus register (Modbus address) values in floating-point data format corresponding to the table in
section 5.1 are based on IEEE754 standard. The response order of data packets is shown as follows.
Low Word
High Byte Low Byte
High Word
High Byte Low Byte
The signed values in the table in section 5.1 are packed in two's complement format. The example is shown as
follows.