Node 3 has two target connections with the send RPIs of 5 ms and 1 ms.
O: Originator
T: Target
HB: Heartbeat
O
O
O
O
T T
T
T
RPI: 200 ms
HB: 200 ms
RPI: 2 ms
HB: 100 ms
RPI: 500 ms
HB: 500 ms
RPI: 5 ms
HB: 100 ms
Node 1
Node 2 Node 3
The total PPS of each node is calculated as follows:
• Total PPS of the Unit Node 1
= 1,000/200 ms + 1,000/2 ms+ 1,000/500 ms (for data)
+ 1,000/200 ms + 1,000/100 ms + 1,000/500 ms (for heartbeat)
= 524 pps
• Total PPS of the Unit Node 2
= 1,000/200 ms + 1,000/2 ms + 1,000/5 ms (for data)
+ 1,000/200 ms + 1,000/100 ms + 1,000/100 ms (for heartbeat)
= 730 pps
• Total PPS of the Unit Node 3
= 1,000/5 ms + 1,000/500 ms (for data)
+ 1,000/100 ms + 1,000/500 ms (for heartbeat)
= 214 pps
In this example, the total PPS of each Unit is below the maximum bandwidth allowed for the Unit, so
data transmission can be successfully performed.
15-1-2
Calculating the Number of Connections
The maximum number of connections per built-in EtherNet/IP port on a CPU Unit is as follows.
• NX701 CPU Unit: 256
• NX102 CPU Unit: 32
• NX1P2 CPU Unit: 32
• NJ-series CPU Unit: 32
The maximum number of connections for a Unit should not be exceeded by the total number of origi-
nator connections, which the Unit opens, and target connections, which other nodes open to the Unit.
Example)
Node 1 has two target connections with Node 2, and opens one originator connection to Node 3. So,
Node 1 has three connections in total.
Node 2 opens two originator connections to Node 1, and one originator connection to Node 3. So,
Node 2 has three connections in total.
Node 3 has one target connection with Node 1, and one target connection with Node 2. So, Node 3
has two connections in total.
In either case, the connections can be successfully opened since the total number of connections is
below the maximum number for a built-in EtherNet/IP port, as shown above.
15 Communications Performance and Communications Load
15-4
NJ/NX-series CPU Unit Built-in EtherNet/IP Port User’s Manual (W506)
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