Table 86: Basic Data Types Of Modbus Protocol; Table 87: List Of The Modbus Functions In The Fieldbus Coupler - WAGO -I/O-SYSTEM 750 Manual

WAGO-I/O-SYSTEM 750
750-882 Media Redundancy ETHERNET Controller
More information
More information on the "Open MODBUS/TCP specification" you can find in the
Internet: www.modbus.org
Therefore the MODBUS protocol based essentially on the following basic data
types:

Table 86: Basic Data Types of MODBUS Protocol

Data type
Discrete inputs
Coils
Input register
Holding register
For each basic data type one or more function codes are defined.
These functions allow digital or analog input and output data, and internal
variables to be set or directly read out of the fieldbus node.

Table 87: List of the MODBUS Functions in the Fieldbus Coupler

Function code
Desig- Value
nation
FC1 0x01
FC2
0x02
FC3
0x03
FC4 0x04
FC5 0x05
FC6 0x06
FC11 0x0B
FC15 0x0F
FC16
0x10
FC22 0x16
.
Length
1 bit
1 bit
16 bits
16 bits
Function
(hex)
Read Coils
Read Discrete
Inputs
Read Holding
Registers
Read Input
Registers
Write Single
Coil
Write Single
Register
Get Comm
Event Counters
Write Multiple
Coils
Write Multiple
Registers
Mask Write
Register
Fieldbus Communication 225
Access method and description
Reading of several output bits
Reading of several input bits
Reading of several input registers
Reading of several input registers
Writing of an individual output bit
Writing of an individual output
register
Communication event counter
Writing of several output bits
Writing of several output registers
Writing of several bits of an
individual output register by mask
Description
Digital inputs
Digital outputs
Analog input data
Analog output data
Access to resources
(R=read/W=write)
R: Process image,
PFC variables
R:
Process image,
PFC variables
R:
Process image,
PFC variables,
internal variables,
NOVRAM
R: Process image,
PFC variables,
internal variables,
NOVRAM
W: Process image,
PFC variables
W: Process image,
PFC variables,
internal variables,
NOVRAM
R: None
W: Process image,
PFC variables
W:
Process image,
PFC variables,
internal variables,
NOVRAM
W: Process image,
PFC variables,
NOVRAM
Manual
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