Omron SYSMAC CJ1W-EIP21 - Manual (Page 290)

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Communications System Section 10-1
10-1-2 Calculating the Number of Connections
The maximum number of connections for the Unit is 32 for the CJ2M and 256
for other CPU Units.
The number of connections must be set to 32 or less for the CJ2M and 256 or
less for other CPU Units combining both connections that the Unit opens as
the originator and connections that are opened from an originator with the
Unit as the target.
Example
Node 1 opens two connections as the target with node 2 and one connection
as the originator with node 3. Therefore, the total is three connections. Node 2
opens two connections as the originator with node 1 and one connection as
the target with node 3. Therefore, the total is three connections. Node 3 opens
one connection as the target with node 1 and one connection as the target
with node 2. Therefore, the total is two connections. In either case, the con-
nections can be opened because the maximum number of connections for the
Unit is less than 32 for the CJ2M and less than 256 for other CPU Units.
Also, if multicast is set, one packet will be sent, but the number of connections
will be consumed.
Example
Node 3 sends one multicast packet to node 1 and node 2. At that time, node 3
opens one connection as the target with node 1 and one connection as the
target with node 2 for a total of two connections. Caution is required because
the number of connections consumed is the same as for unicast connections
even when multicast connections are set.
O
T T
O T
O T
O
Node 1
Node 3
O: Originator
T: Target
Node 2
T
O T
O
Node 1
Node 3
O: Originator
T: Target
Node 2
Multicast
Multicast