Basic Information About Data Link Systems; Master, Local, And Remote I/O Stations - Mitsubishi MELSEC-A Series Reference Manual

1. OVERVIEW
1.2

Basic Information about Data Link Systems

This section gives the basic information for using the MELSECNET and the MELSECNET/
B data link systems.
Read this section carefully before going on to Chapter 2.
1.2.1

Master, local, and remote I/O stations

In a data link system, link modules are classified into master stations, local stations, and
remote I/O stations as shown below:
(1)
(2)
(3)
REMARK
Master stations........... Controls slave stations (local stations and remote I/O
stations) connected to data link system.
Sets link parameter for the MELSECNET data link system
and the MELSECNET/B data link system.
A data link system must contain one master station.
Local stations.............. Controls I/O and special function modules of the host station
in a program of the host station.
Remote I/O stations.... Controls the I/O module and special function module of the
host station in a program of master station via
MELSECNET(/B).
As for the I/O module and special function module
connected to remote I/O station, online I/O module cannot
be replaced.
POINTS
(1) Set the link parameters for the MELSECNET and MELSECNET/B data link
systems to the master stations only.
The link parameters need not be set to the local and remote I/O stations.
(2) When the MELSECNET and MELSECNET/B data link systems are used with
the QnA or AnUCPU, the "number of modules" and "network refresh
parameters" must be set to the master and local stations.
For the network parameter setting method, refer to the operating manual of
the used GPP function software package or GX Developer.
In addition, the QnACPU can confirm the contents of the link special relays
(M9200 to M9255) and link special registers (D9200 to D9255) using the
special relays (SM1200 to SM1255) and special registers (SD1200 to
SD1255).
(3) The software versions of the master station link modules that allow remote I/O
stations to be connected in the MELSECNET/B data link systems are
indicated below.
A1SJ71T21B............ "B" or later
A1SJ71AT21B.......... "A" or later
AJ71AT21B.............. "B" or later
1) *: Online I/O module replacement means replacing an I/O module without
occurrence of "UNIT VERIFY ERROR" while the programmable controller
is ON.
MELSECNET mode MELSECNET
MELSECNET
MELSECNET
Operating Mode
mode
mode
Applicability
1 - 3
MELSECNET/B
MELSECNET
MELSECNET MELSECNET MELSECNET
composite mode mode mode composite mode