Functional Comparisons - Mitsubishi Electric MELSEC-A Series Manual

2
REPLACEMENT OF MELSECNET (II) AND /B (PLC TO PLC NETWORK)

2.3 Functional Comparisons

Item
Cyclic transmission
Transient
transmission
Automatic return
function
Loopback function
Error detection
Self-diagnosis test
function
Description
MELSECNET ( II ) module
MELSECNET/B module
• X/Y are used to perform 1:1
communications between the
master station and local
stations, and the master
station and remote I/O
stations.
• B/W are used to perform
communications between the
master station and all local
stations.
• The LRDP/LWTP instructions
issued from the master station
are used to read/write devices
on the programmable
controller CPU of local
stations.
• Other stations are accessed
from GX Developer connected
to the master station.
• The master station is
accessed from GX Developer
connected to local stations.
When a disconnected local
station returns to normal status,
it is automatically restored and
the data link is resumed.
In the case of an optical loop
system and coaxial loop system,
faulty parts are disconnected
when a fault (e.g. cable
disconnection) occurs, and
normal operation is continued
on operable stations as a result
of the loopback.
Faulty parts are detected by the
data of special relays (M9200 to
9255) and special registers
(D9200 to 9255).
Set the following test items by
the mode setting switch:
• Self-loopback test
• Station-to-station test
• Forward loop/reverse loop
test
: Compatible,
MELSECNET/H module
• LX/LY are used to perform 1:1
communications between the
control station and normal
stations.
• LB/LW are used to perform
communications between the
control station and all normal
stations.
• The READ/WRITE/ZNRD/
ZNWR instructions issued
from the control station are
used to read/write devices on
the programmable controller
CPU of normal stations.
• Other stations are accessed
from GX Works2 or GX
Developer connected to the
control station.
• The control station and other
normal stations are accessed
from GX Works2 or GX
Developer connected to a
normal station.
When a disconnected normal
station returns to normal status,
it is automatically restored and
the data link is resumed.
In the case of an optical loop
system, faulty parts are
disconnected when a fault (e.g.
cable disconnection) occurs,
and normal operation is
continued on operable stations
as a result of the loopback.
Faulty parts are detected by the
data of link special relays (SB0
to 1FF) and link special registers
(SW0 to 1FF).
Set the following test items by
the mode setting switch:
• Self-loopback test
• Internal self-loopback test
• Hardware test
Set the following test items in
the network parameters:
• Station-to-station test
• Forward loop/reverse loop
test
: Partial change required, × : Incompatible
Compat- Precautions for
ibility replacement
Correct the LRDP/LWTP
instructions for reading/
writing devices on the
programmable controller
CPU of other stations to the
READ/WRITE or ZNRD/
ZNWR instructions.
(Refer to Section 2.6.2.)
Change the devices in the
sequence program. (Refer
to Section 2.6.2.)
Set the station-to-station
test and forward loop/
reverse loop test in the
network parameter
settings.
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