Appendix A. Modbus Reference
A.1 Default Communication Settings
Table 10 Default Modbus Serial Communication Settings
Description
Default Value
Serial bit rate
19200
Parity
N
Number of data bits
8
Number of stop bits
2
Modbus device address
240
A.2 Function Codes
Table 11 Modbus Function Codes
Function Code
(Decimal)
Function Code
(Hexadecimal)
Name
Notes
03
03
hex
Read Holding
Registers
Class 0
16
10
hex
Write Multiple
Registers
Class 0
43 / 14
2B
hex
/ 0E
hex
Read Device
Identification
A.3 Data Encoding
In the data registers, the numeric values are available in one or two formats with separate
register addresses: 32-bit IEEE floating point format and/or 16-bit signed integer format.
A.3.1 32-Bit Floating Point or Integer Format
Least-significant 16 bits of floating point or integer numbers are placed at the smaller Modbus
address as specified in Open Modbus TCP Specification, Release 1.0. This is also known as
"little-endian" or "Modicon" word order. Floating point values are represented in standard IEEE
32-bit floating point format.
Appendix A – Modbus Reference
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