Functional Comparisons - Mitsubishi Electric MELSEC-A Series Manual

3
REPLACEMENT OF MELSECNET (II) AND /B (REMOTE I/O NETWORK)

3.3 Functional Comparisons

Item
Cyclic transmission
Transient transmission
Automatic return
function
Loopback function
Error detection
Self-diagnosis test
function
3
- 10
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.
• The RFRP/RTOP instructions
issued from the master
station are used to read/write
the buffer memory of special
function modules at remote I/
O stations.
• Other stations are accessed
from GX Developer
connected to the master
station.
• The master station is
accessed from GX Developer
connected to remote I/O
stations.
When a disconnected remote I/O 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
X/Y are used to perform 1:1
communications between the
remote master station and
remote I/O stations.
• The REMFR/REMTO
instructions issued from the
remote master station are
used to read/write the buffer
memory of intelligent function
modules at remote I/O
stations.
• Other stations are accessed
from GX Works2 or GX
Developer connected to the
remote master station.
• The remote master station is
accessed from GX Works2 or
GX Developer connected to
remote I/O stations.
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:
• Forward loop/reverse loop
test
: Partial change required, × : Incompatible
Compat- Precautions for
ibility replacement
Correct the RFRP/RTOP
instructions for reading/
writing buffer memory on
intelligent function modules
at remote I/O stations to the
REMFR/REMTO
instructions. (Refer to
Section 3.6.2.)
Change the devices in the
sequence program. (Refer
to Section 3.6.1.)
• Set the forward loop/
reverse loop test in the
network parameter
settings.
• Substitute the station-to-
station test with the
forward loop/reverse loop
test.