9
PROGRAMMING
9.3 Program Examples for Use in MELSECNET/H Remote I/O Network
9.3.2 MODBUS(R) device assignment parameters
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9
PROGRAMMING
10
DEDICATED
INSTRUCTIONS
11
TROUBLESHOOTINGAPPENDICESINDEX
(4) Program example
The following is an example of the sequence program required to perform the
communication shown in (2).
(a) Interlock program example for MELSECNET/H
Provide interlocks using the link status of the MELSECNET/H remote master
station (host) and MELSECNET/H remote I/O station (other station).
The example below shows an interlock for a communication program, which uses
the link status (SB47, SB49) of the MELSECNET/H remote master station and the
link status (SW70, SW74, SW78) of the MELSECNET/H remote I/O station
(Station No. 1).
Set the following value as timer constant K .
Reason: To prevent the control from stopping even if the network detects an
instantaneous error due to a cable problem, noise or any other condition
Note that the above "4" and "3" represent standard values.
POINT
For details on interlock programs for the MELSECNET/H remote master station
and MELSECNET/H remote I/O station, refer to the following manual.
Q Corresponding MELSECNET/H Network System Reference Manual
(Remote I/O network)
Figure 9.46 Interlock program example for MELSECNET/H
Table9.10 Value of timer constant K
Baton pass status
(T0, T2)
(Sequence scan time 4) or more
Cyclic transmission status
Parameter communication status
(T1, T3, T4)
(
Sequence scan time 3) or more
SB47: Baton pass status (host)
SB49: Host data link status
SW70: Baton pass status of
each station
SW74: Cyclic transmission status
of each station
SW78: Parameter communication
status of each station
SB20: Module status
Program for MODBUS device assignment : refer to (4) (b) in this section
R
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