Rockwell Automation Ethernet Design Considerations Reference Manual - Manual (Page 84)

84 Rockwell Automation Publication ENET-RM002C-EN-P - May 2013
Chapter 5 Predict System Performance
While you can use the EtherNet/IP node count to select a CompactLogix 5370
controller for your network requirements, most applications use three sets of
calculations to determine performance:
• Identify and Count Connections
• Calculate Packets/Second
• Estimate Maximum Input or Output Times for CIP Connections
ControlLogix Controller Example
This example control system includes these connections:
• The 1756-L73 controller in the local chassis producing one tag that the
1756-L73 controller in the remote chassis consumes
The produced/consumed tags between the local and remote 1756-L73
controllers use an RPI = 20 ms
• One rack-optimized connection between the local controller and the
remote digital I/O modules at an RPI = 20 ms
• One direct connection to each remote analog I/O module at an
RPI = 50 ms.
Figure 8 - Example ControlLogix System over an EtherNet/IP Network
You also can use the EtherNet/IP Capacity Tool described on page 69 to make
performance predictions.
IMPORTANT Each 1756-EN2T communication module in the example control system is
series A, firmware revision 2.003.
For 1756 communication modules, series level and firmware revision
determine the maximum packet rate capacity. For more information, see
Table 13 on page 67 .
Local ControlLogix Chassis Remote ControlLogix Chassis
1756-L73 1756-EN2T
1756-L73 1756-EN2T 2 Analog I/O
Modules 3 Digital I/O
Modules