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What is the Application Response Time of 140CRA31908 (S908)?

Published date: 25 July 2019

Issue
Quantum and M580 systems use different methods to manage I/O points. In a M580 system, the CRP communicates with the 140CRA31908 module that is scheduled by the CPU over Ethernet/IP and in a Quantum System, the CPU schedules the CRP directly over the backplane. It is important to understand the Application Response Time (ARP) of both systems to tune it properly. 

Product Line
Control Expert, M580, 140CRA31908   

Environment
Control Expert v14, BMEP586040 v2.70, 140CRA31908 v2.30

Resolution
Quantum and M580 systems use different methods to manage I/O points and the application response time:
  • Quanutm: Communicaiton exchanges between an S908 CRP module and a Quanutm CPU are done periodically within the cycle time and sequentially remote drop by remote drop. That means the Quantum CPU does not scan the next Quantum S908 remote drop until data for the current remote drop are available. It also means the CPU does not execute the application until all remote drops are refreshed.
  • M580: In an M580 syste, the input data are sent at a predetermined time interval based on the request paclet interval (RPI). The RPI is set (by default) to one-half of the cycle time (if periodic) to synchronize the data with the task.
So, Quantum S908 ART:



So, M580 S908 ART:



Thanks to M580 additional processing power, we estimate that the cycle execution can be reduced from three to five times compared to Quantum.
P.S.: Detailed information may be found on "Modicon Quantum 140CRA31908 Adapter Module Installation and Configuration Guide"

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