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Section
Network Configuration Restrictions
Note
3-2
3-2
1. Multi-drop connections with thick cables cannot be used with the connectors
supplied with the Unit because the cables are too thick. Use the following
connectors for multi-drop connections with thick cables. (For further details,
refer to Section 5 Connectable Devices.)
XW4B 05C4-T-D (w/o set screw) (made by OMRON)
TMSTB 2.5/5-ST-5.08 AU (w/o set screw) (made by Phoenix Contact)
The connector specifications are the same for both cables.
These connectors cannot be used with the Master Unit or CQM1 I/O Link
because they may come into contact with the Unit in the adjacent slot. In this
case, use a T-branch Tap.
2. When using thick cable, the cable may pull out of the connector depending
on the strength of the cable. Follow 7-3 Connecting Communications
Cables, when connecting communications cables.
Network Configuration Restrictions
3-2-1 Maximum Network Length
The length of the network is longest at either the distance between the two most
distant nodes or at the distance between the Terminating Resistors.
Longest distance is the maximum network length
Terminal-block
Terminating Resistor
T-branch Tap with
Terminating Resistor
Node
Length of
drop line
Node
Length of
drop line
Node
Communications
power supply
Node
There are two types of cables: Thick cables and thin cables. The thick cables are
relatively hard and inflexible, but they protect against signal attenuation and can
be used for relatively long communications distances. The thin cables are soft
and flexible, but they do not protect as well against signal attenuation and are not
suited to long communications distances.
The maximum length of a network thus depends on the type of cable that is used,
as shown in the following table.
Cable type
Maximum network length
Thick cables (5-wire)
500 m
Thin cables (5-wire)
100 m
Note a) If the length of the network is 100 meters or less, the thin cables
can be used for the trunk line. When using thin cables for the trunk
line, be sure that communications power supply conditions are
met.
b) The length of the network is also restricted by the baud rate used.
Even with thick cables, the length of the network will be restricted if
the baud rate is set to anything but 125 kbps. Refer to 3-2-4 Baud
Rate and Communications Distance.
Note Combining Thick and Thin Cables
The most distant nodes can also be connected by a combination of thin and thick
cables. When these cables are combined, the following conditions must be met
and the maximum network length will be shorter than when only thick cables are
used. Also, when combining cables, be sure that the maximum current capacity
of the cables is not exceeded. Refer to Section 6 Communications Power Supply.
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