Rockwell Automation Ethernet Design Considerations Reference Manual - Manual (Page 98)

98 Rockwell Automation Publication ENET-RM002C-EN-P - May 2013
Chapter 5 Predict System Performance
Estimate the Maximum Input or Output Times for CIP Connections
Calculate the worst-case, maximum input (I/O to controller) or output
(controller to I/O) times for CIP connections in your system.
For a Rack-optimized Connection, the maximum input or output time for a
CIP connections is estimated as follows:
T
MAX (Rack-optimized)
= RPI = 20 ms
For the Direct Connect Analog Modules, assume non-isolated modules with
the real-time sampling (RTS) rate equal to the RPI, that is, 50 ms. Therefore, the
maximum input or output time is estimated as follows:
T
MAX (Analog Non-Isolated)
= 2RTS
= 2 x 50 ms = 100 ms
Isolated modules have an RTS rate of 1RTS.
For a Produced or Consumed Tag, the maximum input or output time is
estimated as follows:
T
MAX (Produced/Consumed Tag)
= 1RPI
= 1 x 20 ms = 20 ms
Assume that these times are acceptable for the example application. If you find
that the times for your system are too slow, you can make adjustments to operate
at faster RPIs. This can require choosing I/O modules that operate at faster data
rates, adding more EtherNet/IP communication modules, and/or other changes
as outlined in
step 5 on page 81 .
No further modifications have been made, so the system is complete.