Rockwell Automation 1756-DHRIO_DHRIOXT ControlLogix Data Highway Plus-Remote I/O Communication Interface Module - Manual (Page 168)

168 Rockwell Automation Publication 1756-UM514C-EN-P - June 2014
Appendix B Application Guidelines and Tips
Remote I/O Performance:
ControlLogix Controllers
versus PLC-5 Controllers In the following figure, block transfer write messages are sent from a
ControlLogix controller (via the 1756-DHRIO or 1756-DHRIOXT module)
to a 1771-DCM over cached remote I/O connections.
The following figure illustrates the differences between using cached remote I/O
connections with the 1771-DCM module and using PLC-5 connections with
the 1771-DCM module.
1756-DHRIO
1771 Chassis containing:
PLC-5/60 processor
1771-DCM module
Remote I/O
41284
ControlLogix Controller
0
20
Number of Nodes per Block Transfer Write Messages
1 2 3 4 5 6 7 8 9 10 11 12 13
230K Cached
40
60
80 115K Cached
57.6K Cached
230K Cached
115K Cached
57.6K Cached
14 15
100
120
Block Transfer Write Messages
per Second
All 15 Block Transfer Write messages were on one channel.
Each Block Transfer Write message was 40 words in size.