Delta RMC101 - Manual (Page 360)

RMC100 and RMCWin User Manual
5-110
6 17.0
ms
7 20.0
ms
8 23.0
ms
9 25.0
ms
10 28.0
ms
* The 1756-ENET has enough bandwidth for a single connection with an RPI as low as 3.0 ms, but the
RMC does not support that low of an RPI.
If the 1756-ENET is controlling other non-RMC I/O, the bandwidth required by these other
connection will also need to be taken into consideration. The EtherNet/IP Performance and
Application Guide
covers these more advanced configurations.
In addition to the 1756-ENET and RMC ENET load limitations, the effect of collisions needs to be
considered. See Predicting the Effect of Collisions for details.
Example:
Suppose one ControlLogix will be controlling three RMCs. The intended RPI is 6.0 ms. Therefore the
bandwidth in frames/second is computed as follows:
Frames/Second = (2 x connections) / RPI
= (2 x 3) / 0.006s
= 1000
This is over both the 720 frames/second we recommend and the 810 frames/second that Rockwell
recommends. Therefore, you have three options:
• Increase the RPI of one or more of the RMCs until the bandwidth is below 720. Raising each to
9.0 ms does this.
• Replace the 1756-ENET with the 1756-ENBT. The bandwidth on the 1756-ENBT (see
Evaluating the Load on the 1756-ENBT) is limited to 5000 frames/second, and easily handles
this load.
• Use two 1756-ENET modules: one will control two RMCs with RPIs of 6.0 ms (667
frames/second) and the second will control one RMC with an RPI of 6.0 ms (333
frames/second). Both are within the recommended limits.
Example:
Suppose one ControlLogix will be controlling three RMCs again, but this time one RMC needs an RPI
of 5.0 ms, and the other two RMCs need an RPI of 15.0 ms. To compute the bandwidth requirement
on the ControlLogix, compute the bandwidth required at each RPI, and sum them together: