M580 HSBY CPU Scan time

[prathaps]

How to reduce the H586040 Scan time, the scan time of CPU is exceeding the maximum limit set in the mast task.

[Ricard]

Hello Prathaps, 

I think that you want is increase the scan period of the MAST task, isn't you?

this topic is very important to have a good health of our M580 HSBY System. If we have a lot of the overruns probably we don't have our system synchronization.

If task cycle times are set large enough, the HotStandby M580 CPU can process the data produced by the system in a single scan. If the configured task cycle time is less than the required processing time, the CPU will force an overrun (Overrun %S19) of the task.

There are two main conditions that must be met to avoid overflow events. Using the formulas below, you can calculate the minimum task times for your system and avoid a task overflow situation.

Condition 1: The I/O configuration.

The general formula for a multitasking application is:
(nº of RIO stations using MAST task/MAST cycle time) + (nº of RIO drops using SAFE task/SAFE cycle time) + (nº  of RIO stations using FAST task/FAST cycle time) <1.5

If DIO devices have been configured, increase the minimum

Example:
A local rack with a CPU with 10 RIO drops that only uses the MAST task. The minimum MAST cycle time is equal to: 10 / TMAST <1.5 or TMAST >6.7 ms

Condition 2: PAC processor load.
Each task uses a percentage of the PAC resources, here called task bandwidth (TaskBW).
It is considered that the bandwidth of all tasks should not exceed 80% so that the PAC can perform other intermittent system operations, for example, online modifications.
MastBW + SafeBW + FastBW <0.8

I could be talking about this topic at length, ... if you want to know more, consult the M580 HSBY documentation

I'm attaching one of the documentation of M580 HSBY

Modicon M580 - Hot Standby, System Planning Guide for Frequently Used Architectures

https://www.se.com/us/en/download/document/NHA58880/

I hope I could help you

[Michael_Chan]

Hi Prathaps,

Have a look at this knowledge base article to understand how M580 HSBY CPU scan time works.

How Can I Optimize Cycle Time of M580 Redundant System? 

Hope this article can help you.

[prathaps]

Thanks for support.. But Iam not able to open the link

[Michael_Chan]

I guess you need to register on the website. Anyway, here's the attached file.