Technical data

144 • MODBUS Functions
General
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
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 controller.
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.
Function code
hexadec.
Function
Access method and
description
Access to resources
FC1:
0x01 Read Coils Reading of several
single input bits
R: Process image, PFC variables
FC2:
0x02 Read Input
Discretes
Reading of several
input bits
R: Process image, PFC variables
FC3:
0x03 Read Multiple
Registers
Reading of several
input registers
R: Process image, PFC variables,
internal variables, NOVRAM
FC4:
0x04 Read Input
Registers
Reading of several
input registers
R: Process image, PFC variables,
internal variables, NOVRAM
FC5:
0x05 Write Coil Writing of an
individual output bit
W: Process image, PFC variables
FC6:
0x06 Write Single
Register
Writing of an
individual output
register
W: Process image, PFC variables,
internal variables, NOVRAM
FC 11:
0x0B Get Comm
Event
Counters
Communication
event counter
R: None
FC 15:
0x0F Force Multiple
Coils
Writing of several
output bits
W: Process image, PFC variables
FC 16:
0x0010 Write Multiple
Registers
Writing of several
output registers
W: Process image, PFC variables,
internal variables, NOVRAM
FC 22:
0x0016 Mask Write
Register
W: Process image, PFC variables,
NOVRAM
FC 23:
0x0017 Read/Write
Registers
Reading and writing
of several output
registers
R/W: Process image, PFC variables,
NOVRAM
Tab. 6-1: List of the MODBUS Functions in the Fieldbus Controller
To execute a desired function, specify the respective function code and the
address of the selected input or output data.