Omron CJ1W-EIP21 User Manual

• Press the cable connector in firmly until it locks into place at both the

switching hub and the EtherNet/IP Unit.

• Do not lay the twisted-pair cable together with high-voltage lines.

• Do not lay the twisted-pair cable near devices that generate noise.

• Do not lay the twisted-pair cable in locations subject to high temperatures

or high humidity.

• Do not lay the twisted-pair cable in locations subject to excessive dirt and

dust or to oil mist or other contaminants.

• Do not ground the switching hub in the same location as a drive-system

component such as an inverter.

• Always use a dedicated power supply for the switching hub’s power sup-

ply. Do not use the same power supply used for other equipment, such as
an I/O power supply, motor power supply, or control power supply.

• Before installation, check the switching hub’s environment-resistance

specifications, and use a switching hub appropriate for the ambient condi-
tions. Contact the switching hub manufacturer for details on switching
hub’s environment-resistance specifications.

Connect two hubs to each other as follows: Connect an MDI port to an MDI-X
port with a straight cable; connect two MDI ports with a cross cable; and
connect two MDI-X ports with a cross cable. 

It is very difficult to distinguish cross cables and straight cables by appear-
ance. Incorrect cables will cause communications to fail. We recommend
using cascade connections with straight cables whenever possible.

Some switching hubs can automatically distinguish between MDI and MDI-X.
When this kind of switching hub is being used, straight cable can be used
between switching hubs.

Note Adjust the link settings of the EtherNet/IP Unit or built-in EtherNet/IP port to

match the communications settings of the connected switching hub. If the set-
tings do not match, the link will become unstable and prevent normal commu-
nications. The following table shows the allowed settings for each switching
hub communications mode.

MDI-X port 
(cross)

Switching 
Hub

Switching 
Hub

Switching 
Hub

Straight cable
Cross cable

Switching 
Hub

MDI ports

Auto-negotiation

Best

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OK

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OK

10 Mbps 
(fixed)

Full duplex

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OK

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Half duplex

OK

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OK

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