Mitsubishi Electric Melsec A Series - Page 43

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REPLACEMENT OF MELSECNET (II) AND /B (PLC TO PLC NETWORK)
2
(3) Comparison between MELSECNET/B module (twisted pair) and MELSECNET/H module
(optical loop/coaxial bus)
: Compatible, : Partial change required, × : Incompatible
Item
Specifications
Compat-
ibility
Precautions for
replacement
MELSECNET/B module MELSECNET/H module
Twisted pair
Optical loop
(QJ71LP21-25)
Coaxial bus
(QJ71BR11)
Maximum
number of
link points
per network
X/Y
Max. 2048 points and max. number of I/O
points of CPU module on master station
(MELSECNET/10 mode),
(MELSECNET/H mode),
(MELSECNET/H extended mode) 8192
points
B
• (MELSECNET mode) 1024 points
• (MELSECNET II mode),
(MELSECNET II composite mode) 4096
points
• (MELSECNET/10 mode) 8192 points
• (MELSECNET/H mode),
(MELSECNET/H extended mode)
16384 points
W
• (MELSECNET mode) 1024 points
• (MELSECNET II mode),
(MELSECNET II composite mode) 4096
points
• (MELSECNET/10 mode) 8192 points
• (MELSECNET/H mode),
(MELSECNET/H extended mode)
16384 points
Maximum number
of link points per
station
• (MELSECNET mode) 1024 bytes
• (MELSECNET II mode),
(MELSECNET II composite mode)
Link parameter first half: 1024 bytes
Link parameter second half: 1024 bytes
• (MELSECNET/10 mode),
(MELSECNET/H mode)
{(LY + LB)  8 + (2 × LW)} 2000 bytes
• (MELSECNET/H extended mode)
{(LY + LB)  8 + (2 × LW)} 35840
bytes
When the number of bytes
exceeds 2000, mount two
modules having the same
network No., or set all
modules on the network in
the MELSECNET/H
extended mode.
Communication
speed
125kbps/250kbps/500kbps/1Mbps
25Mbps/10Mbps -
- 10Mbps
Number of stations
connected in one
network
32 stations (master station: 1,
local station + remote I/O station: 31)
64 stations (control
station: 1
normal station: 63)
-
Set the remote I/O network
to a separate network.
-
32 stations (control
station: 1
normal station: 31)
Set the remote I/O network
to a separate network.
Applicable cable Shielded twisted pair cable
SI optical cable
H-PCF optical cable
Broad-band H-PCF
optical cable
QSI optical cable
-
A new optical cable has to
be installed.
-
3C-2V
5C-2V
A new coaxial cable has to
be installed.
Overall distance
125kbps: 1200m
250kbps: 600m
500kbps: 400m
1Mbps: 200m
30km -
-
3C-2V: 300m
5C-2V: 500m
Either use an A6BR10/
A6BR10-DC type repeater
unit, or configure a
separate network.
Distance between
stations
125kbps: 1200m
250kbps: 600m
500kbps: 400m
1Mbps: 200m
Refer to Section
2.2.2.
-
When 1200 m is required,
use GI optical cables for all
optical cables, and use
QJ71LP21G as the
module.
-
3C-2V: 300m
5C-2V: 500m
Either use an A6BR10/
A6BR10-DC type repeater
unit, or configure a
separate network.
Maximum number
of networks
-239
New MELSECNET/H
parameter (mandatory)
Communication
method
Half duplex bit serial method Token bus method
Nothing to be noted though
the communication method
differs.
Transmission
method
Single bus
Duplex loop -
Nothing to be noted though
the transmission method
differs.
- Single bus