AC800m HI: Is it safe to add additional DO880 and DI880 modules to a TB840A in a running SIL2 system?

Here's the setup: one non-redundant PM865K01 controller running a SIL2 application, with non-redundant remote IO on an optical ModuleBus ring (ie., SM811/PM865K01 -> TB825 -> (fiber) -> TB825 -> one TB840A with several DI880 and DO880)

Now, can I add and configure additional DI880 and DO880 modules to the TB840A without interrupting the existing system? (There are no time-critical tasks in the controller, so briefly halting the application should be fine. But the state of existing IO-channels must not change.)

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rewinixux Rank: 1165

Asked 7 months ago

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For AC800M High integrity, it is recommended to maintain Cyclic load of 50% and System load of 90%.
SO you need to check your existing Cyclic as well system load.

Cycle load will increase based on Application size, task interval , IAC variables used

System load will increase when there is increase in cycle load along with IO Scanning etc.

So by having this information, you shall make analysis to add new modules or not .

Also try to have the Power calculation document updated with new module and verify enough power is there else you may get drip of it.

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