Appendix A. Modbus Reference
A.1 Default Communication Settings
The following table lists the default Modbus serial settings of devices ordered with the Modbus
configuration option.
Table 23 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
Serial delay 0
Communication mode Modbus RTU
A.2 Function Codes
Table 24 Modbus Function Codes
Function Code (Decimal) Function Code (Hexadecimal) Name
03 03
hex
Read Holding Registers
16 10
hex
Write Multiple Registers
43 / 14 2B
hex
/ 0E
hex
Read Device Identification
A.3 Data Encoding
A.3.1 32-Bit Floating Point Format
Registers using "32-bit float" data format are encoded using the "binary32" encoding defined
in IEEE 754 (also known as "single-precision floating point format").
The least significant 16 bits of a floating point number are placed at the Modbus register listed
in the table, while the most significant 16 bits are placed in the register with number/
address + 1, as specified in Open Modbus TCP Specification, Release 1.0. This is also known as
"little-endian" or "Modicon" word order.
Appendix A – Modbus Reference
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