Modbus Functions; General - WAGO 750-341 Manual

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General

Application Protocols

6 MODBUS Functions

6.1 General
Various MODBUS functions from the OPEN MODBUS / TCP
SPECIFICATION are found in the application layer of the WAGO
ETHERNET fieldbus coupler.
More information
More information on the OPEN MODBUS / TCP SPECIFICATION you can
find in the Internet: www.modbus.org.
These functions allow digital or analog input and output data, and internal
variables to be set or directly read out of the fieldbus node.
FC1:
FC2:
FC3:
FC4:
FC5:
FC6:
FC 11:
FC 15:
FC 16:
FC 22:
FC 23:
Tab. 6-1: List of the MODBUS Functions in the Fieldbus Coupler
Note
Not all internal variables can be read in the block with the function codes
FC 3 and FC 16.
Function code
Function
hexadec.
0x01 Read Coils
0x02 Read Input
Discretes
0x03 Read Multiple
Registers
0x04 Read Input
Registers
0x05 Write Coil
0x06 Write Single
Register
0x0B Get Comm
Event
Counters
0x0F Force Multiple
Coils
0x0010 Write Multiple
Registers
0x0016 Mask Write
Register
0x0017 Read/Write
Registers
Access method and
description
Reading of several R: Process image
single input bits
Reading of several R: Process image
input bits
Reading of several R: Process image, internal variables
input registers
Reading of several R: Process image, internal variables
input registers
Writing of an W: Process image
individual output
bit
Writing of an W: Process image, internal variables
individual output
register
Communication R: None
event counter
Writing of several W: Process image
output bits
Writing of several W: Process image, internal variables
output registers
W: Process image
Reading and R/W: Process image
writing of several
output registers
Access to resources
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP