Mitsubishi Electric Melsec A Series - Page 42

REPLACEMENT OF MELSECNET (II) AND /B (PLC TO PLC NETWORK)
2 - 5
2
(2) Comparison between MELSECNET (II) module (coaxial loop) and MELSECNET/H
module (coaxial bus)
: Compatible, : Partial change required, × : Incompatible
Item
Specifications
Compat-
ibility
Precautions for
replacement
MELSECNET ( II ) module MELSECNET/H module
Coaxial loop 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)
First half: 1024 bytes
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
1.25Mbps 10Mbps
Number of stations
connected in one
network
65 stations (master station: 1,
local station + remote I/O station: 64)
32 stations (control station: 1, normal
station: 31)
• Set the remote I/O network
to a separate network.
• For the 33th station,
configure a separate
network.
Applicable cable
3C-2V
5C-2V
When using existing cables,
the overall distance and
distance between stations
becomes shorter.
Overall distance
3C-2V: 10km
5C-2V: 10km
3C-2V: 300m
5C-2V: 500m
Either use an A6BR10/
A6BR10-DC type repeater
unit, or configure a separate
network.
Distance between
stations
3C-2V: 500m
5C-2V: 500m
3C-2V: 300m
5C-2V: 500m
When using the 3C-2V, use
the A6BR10/A6BR10-DC
type repeater unit.
Maximum number
of networks
- 239
New MELSECNET/H
parameter (mandatory)
Communication
method
Half duplex bit serial method Token ring method
Nothing to be noted though
the communication method
differs.
Transmission
method
Duplex loop Single bus
Nothing to be noted though
the transmission method
differs.
Modulation
method (Encoding
method)
(Modulation method) CMI method (Encoding method) Manchester code
Nothing to be noted though
the modulation method
differs.
Transmission
format
HDLC standards (frame format)
Error control
system
CRC(X
16
+X
12
+X
5
+1) and retry by a time over
RAS function
• Loop-back function due to error
detection or broken cable
• Diagnostic function for checking local
link lines
Diagnostic function for checking local link
lines
The loopback function cannot
be used on a coaxial bus
system. To use the loopback
function, using an optical loop
system is recommended.
Number of
occupied I/O
points
CPU integrated type: 0 point,
Standalone:32 points per slot (I/O
assignment: special 32 points)
32 points per slot (I/O assignment: intelli.
32 points)
When replacing from a CPU
integrated type, an additional
slot (32 points) is required.