Siemens UL 489 Operating Instructions Manual page 171

Modbus RTU Functionality
Transmission Protocol
The COM16 module operates in the RTU transmission mode. ASCII transmission mode is not supported.
Overview of supported Functions
The COM16 module provides the following Modbus RTU function codes for accessing the data contained in the WL circuit breaker.
FC Name
02: Read Discrete Inputs
01: Read Coils
05: Write Single Coil
15: Write Multiple Coils
04: Read Input Registers
03: Read Holding Registers
16: Write Multiple Registers
07: Read Exception Status
08: Diagnostics
11: Get Comm Event Counter
12: Get Comm Event Log
Description
Reads the state of the Bits in the Status Register
Reads the state of multiple Control Bits and Extra Flags
Sets the state of a single Control Bit or Extra Flag
Sets the state of multiple Control Bits and Extra Flags
Reads the Basic Data Registers. Three Basic Types (1, 2 and 3) are supported.
Reads a complete data set.
Writes a complete data set.
Reads the state of eight Exception Status bits
Function provides a method for checking the communication between the master
and the slave
Returns a status word and an event count from the communications event counter
Returns a status word, event count, message count, and a field of event bytes
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