Modbus Function Codes - Siemens SITRANS F series Operating Instructions Manual

A.7

Modbus function codes

Table A- 6 General Modbus settings
Function code Command text
01 Read Coils
02 Read Discrete Inputs
03 Read Holding Registers
04 Read Input Registers
05 Write Single Coil
06 Write Single Register
07 Read Exception Status
08 Diagnostics
15 Write Multiple Coils
16 Write Multiple Registers
17 Report Slave ID
23 Read/Write Multiple Registers
Function code 7 (Read exception status)
The device provides the content of the parameter Global alarm status as exceptions.
Function code 8 (Diagnostics)
The diagnostics function provides means for checking the communication between
MODBUS master and slave. The function uses a sub-function code to select the
functionality.
The following sub-function codes are supported:
Sub-function code Name
0 Return query data
1 Restart communications option
Function code 17 (Report Slave ID)
The transmitter will respond to a Report Slave ID request from the master by giving
information about device type, vendor, and firmware version in a format as shown:
Response
Slave address 1 byte
Function code 1 byte
SITRANS F Ultrasonic flowmeters FST030 (Modbus)
Operating Instructions, 08/2017, A5E37367739-AC
Description
Reads the status of single bit(s)
Reads the status of single input bit(s)
Reads the binary content of multiple 16-bit registers
Reads the binary content of multiple 16-bit registers
Writes a single on/off bit
Writes the binary content of single 16-bit register
Delivers the global alarm status of the device
Provides a series of tests for checking the communication
system
Writes multiple on/off bits
Writes the binary content of multiple 16-bit registers
The device will respond to a Report Slave ID command (com-
mand 17) request from the master by giving information about
device type, vendor, and revision level
Combined Write Multiple Registers / Read Holding Registers
call
Description
The data passed in the request data field will be returned
(looped back) in the response. The entire response message
should be identical to the request.
After having restarted the communication, select the baudrate,
framing or Modbus address to get access to the device again.
17
Modbus communication
A.7 Modbus function codes
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