Omron CS1W-CRM21 - Page 25

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CompoNet Networks Section 1-1
Communications Cables CompoNet Networks use Round Cable I, Round Cable II, Flat Cable I (DCA4-
4F10 Standard Flat Cable), and Flat Cable II (DCA5-4F10 Sheathed Flat
Cable) for Communications Cables.
Master Unit The Master Unit manages the CompoNet Network and transfers I/O data
between the PLC and the Slave Units.
There is only one Master Unit per network. The Master Unit must be con-
nected to the end of the trunk line.
Slave Units Some Slave Units receive output data from the Master Unit across the Com-
poNet Network and output it. Other Slave Units send data that has been input
across the network to the Master Unit. There are two types of Slave Unit
according to the I/O capacity of the Slave Unit.
• Word Slave Units: A Word Slave Unit is allocated 16 bits (i.e., 16 I/O
points) in the I/O memory of the CPU Unit.
• Bit Slave Units: A Bit Slave Unit is allocated 2 bits (i.e., 2 I/O points) in the
I/O memory of the CPU Unit.
Repeater Unit Using Repeater Units enables expanding network connections as follows:
• Extending the Communications Cable
• Increasing the number of nodes (Units)
• Creating long-distance T-branches from the trunk line and sub-trunk lines
(See note.)
• Converting between different types of cable (round cable I, round cable II,
Flat Cable I, and Flat Cable II)
A sub-trunk line downstream from a Repeater Unit can be connected with the
same communications specifications (i.e., distances and number of Slave
Units) as the trunk line.
Up to 64 Repeater Units can be connected per network (i.e., per Master Unit).
When Repeater Units are connected in series from the Master Unit, up to two
layers can be created.
Note The physical layer is not connected across a Repeater Unit. The
connection is thus different from a branch connection, which
branches the same physical layer.
Terminating Resistors With a CompoNet Network, the Master Unit is located at one end of the trunk
line and a Terminating Resistor is connected to the other end of the trunk line.
If Repeater Units are used, each Repeater Unit is treated like a Master Unit,
i.e., Terminating Resistor is connected to the most remote end of the sub-
trunk line downstream from the Repeater Unit.
Note A Terminating Resistor reduces signal bouncing to stabilize com-
munications and must always be connected to the most remote end
of the network lines below the Master Unit and each Repeater Unit.
Always connect a Terminating Resistor to ensure the quality of the
transmission path.
Trunk Lines and Branch
Lines
The trunk lines and branch lines in a CompoNet Network are defined as fol-
lows:
• Trunk line: The transmission path between the Master Unit and the Termi-
nating Resistor.
• Sub-trunk line: The transmission path between the Repeater Unit and the
Terminating Resistor (when a Repeater Unit is used)
• Branch line: The transmission path created using a T-branch from the
trunk line or sub-trunk line.