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This FAQ has been written for NEAL (North East Africa and Levant) region. If you are looking for information for another region, please select the correct country from the top-left dropdown in the page and 'Navigate to Browse FAQs' in the Support menu.

How to calculate the scan time of Hot Stand-By (HSBY) system in Modicon Quantum range.

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.