Delta RMC101 - Manual (Page 359)

Ethernet 5.2
Communications 5-109
Connections RPI
1 5.0
ms
2 7.0
ms
3 9.0
ms
4 12.0
ms
Example:
Suppose you will be establishing one I/O connection to an RMC, and the RPI will be 15.0 ms. Use the
formula above to compute the RMC ENET load:
Frames/Second = (1 + connections) / RPI
= (1 + 1) / 0.015s
= 133
This is only 27% of the RMC ENET bandwidth. Therefore, a lot of processing time will be available for
handling non-I/O traffic such as from RMCWin and ControlLogix MSG blocks.
5.2.6.3.7.3 Evaluating the Load on the 1756-ENET
Rockwell Automation's EtherNet/IP Performance and Application Guide (Pub. No. ENET-
AP001C-EN-P) describes how to compute the 1756-ENET loading in detail. When using the
worksheets in that manual, consider each RMC connection a "Rack Optimized Connection." That
is, the Frames/Second required for an RMC in the 1756-ENET is computed the same as Rack
Optimized Connections:
Frames/Second = (2 x connections) / RPI
The 1756-ENET module's bandwidth is limited to 900 frames/second. Rockwell recommends that
no more than 90% (810 frames/second) be allocated to I/O connections. From our independent
testing, we recommend allocating no more than 80% (720 frames/second) for I/O connections.
If a 1756-ENET will be used only for controlling RMCs and each RMC has the same RPI, then the
following chart can be used to determine the minimum RPI allowed for the number of RMCs:
RMCs Min
RPI
1 5.0
ms*
2 6.0 ms
3 9.0 ms
4 12.0
ms
5 14.0
ms