Frequently asked questions
How to calculate the scan time of Hot Stand-By (HSBY) system in Modicon Quantum range.
FA21086
31 December 2021
Considering the Hot Stand-By system, the scan time mainly comes from the addition of three parts:
Part 1: User application logic execution time, with an additional data transfer time from Primary to Stand-By communication load RIO management.
Part 2: Depending on the communication load on Modbus, there will be around 1 or 2 ms needed to answer to Modbus read/write requests coming from Modbus network.
Part 3: The scan time needed for RIO management is 2.5 ms
Example:
For 100kb data to transfer from Primary to Stand-By and user logic execution time being less than 6ms, then the scan time of Part 1 is 15 ms (using last CPU firmware version v2.50 or v2.60). Thus ultimately the average scan time will be roughly 19ms for the given example.
For 100kb data to transfer from Primary to Stand-By and user logic execution time being less than 6ms, then the scan time of Part 1 is 15 ms (using last CPU firmware version v2.50 or v2.60). Thus ultimately the average scan time will be roughly 19ms for the given example.