Omron NX-EIC202 - Page 252

10 I/O Refreshing
10 - 4
NX-series EtherNet/IP Coupler Unit User’s Manual (W536)
The number of packets transferred each second is called the used bandwidth or PPS (packets per sec-
ond).
The PPS is calculated from the RPI and heartbeat as follows for each connection:
PPS used in a connection (pps) = (1,000 ÷ RPI (ms)) + (1,000 ÷ Heartbeat transmission period (ms))
Use the following equation to calculate the total number of packets transferred by each Ether- Net/IP
port (Unit) in 1 second.
EtherNet/IP port’s total PPS = Total PPS of target connections
The maximum number of packets that the EtherNet/IP Coupler Unit can transfer in 1 second (called the
allowed Unit bandwidth) is 1,000 pps, so set the connection below this maximum value.
Example:
Node 1 has both originator and target connections, with send RPI of 200 ms and 2 ms, and receive RPI
of 500 ms.
Node 2 has originator connections only, with receive RPIs of 200 ms, 2 ms, and 5 ms.
Node 3 has target connections only, with send RPIs of 5 ms and 1 ms.
Each node’s total PPS is calculated as follows:
• Total PPS of node 1’s Unit
= 1000 / 200 ms + 1000 / 2 ms + 1000 / 500 ms (for data)
+ 1000 / 200 ms + 1000 / 100 ms + 1000 / 500 ms (for heartbeat)
= 524 pps
• Total PPS of node 2’s Unit
= 1000 / 200ms + 1000 / 2 ms + 1000 / 5 ms (for data)
+ 1000 / 200ms + 1000 / 100 ms + 1000 / 100 ms (for heartbeat)
= 730 pps
• Total PPS of node 3’s Unit
= 1000 / 5 ms + 1000 / 500 ms (for data)
+ 1000 / 100 ms + 1000 / 500 ms (for heartbeat)
= 214pps
All of the Units are within the allowed Unit bandwidth (refer to appropriate EtherNet/IP Unit specifica-
tion), so they can transfer data.
Requested Packet Interval (RPI) and Bandwidth Usage (PPS)
O: Originator
T: Target
HB: Heartbeat
O
O
O
O
TT
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