Emerson Exchange 365

You can "wire" to it.

If you set the Parameter type to "MODE", the Target, Actual, and Normal mode all get written to the Param.

In reply to Travis Neale:

Hi Neale

Even if you wire it up to mode parameter of the DC block still you got to write in the mode parameter which you will connect to DC block.

In reply to Manzoor:

Basically i want to avoid the writes to the mode.target parameter

In reply to Manzoor:

Do I understad you correctly:  You want to change the MODE.TARGET of a block without writing to it?

In reply to Travis Neale:

Yes I would like to change the mode without using the action or calculation block for writing into it. I would like to do something like by wiring to the mode parameter of the DC block. Is it possible?.

In reply to Manzoor:

What do you invision "changing" the mode.target?  Logic, or user interaction?

In reply to Travis Neale:

I would say both. The possibility of having user interaction &  "changing" it through logic should be available as it adds to the flexibility to the design.In one of your previous post you wrote that we could do it by wiring the mode parameter of the DC block to a parameter with mode attribute. I tried it but still you have to write in the mode parameter & that we can do only through action or calculation block.

In reply to Ole Abildgaard:

This looks like a good idea.But still to "set" the integer parameter you would need to write in the parameter.Basically I would like to minimize or eliminate the "writes" & this will still require me to write a number 16 or 32 in the parameter instead of in the mode parameter of the DC block. I will surely try this method tomorrow when I have system in front of me. Have you tried  or tested this before??

In reply to Manzoor:

In all "real" applications, I have made, I use CALC blocks, ACTION blocks or sequence actions for this and do not have a problem with that.

I have only just briefly tested this on my stand alone simulate pro+. And I am not sure if Emerson would support the "solution" to your request.

The parameter wired into the MODE parameter of a DC block may be an internal reference to the result of a calculation. The value does not have to be written from a CALC or ACTION block. But then, even a wired input is a form of writing a value. And in the end, you have to write some way if you want to change the target mode.

The value of the linked parameter wired into an input MODE parameter on a DC block, apparently can be integer or float, but it does not work if the parameter is with status. Hence, you have to strip the status from the calculated result, if this is the way you choose to go.

In reply to Ole Abildgaard:

The MODE is not something that typically changes frequently, and writing via a wired parameter would create a continuous write to the mode.target as desribed in previous inputs.  with a wired connection, a manual write by the operator would be overridden by the wired value and Operator writes would no longer be possible.

As Ole mentions, expressions are typically used because there is usually a need to determine when the Mode change is needed and a one time action (MODE.TAGET := xxxxx) is all that is needed.  SFC actions also come with the delay and confirm expressions to ensure the write is only performed if needed and is properly confirmed.  If MODE.ACTUAL is not in the proper state, writes to the expected parameter may fail, and having continuous writes does not provide the checks for successful completion.

If you want to lock the MODE, you can look at dynamically adjusting the permitted modes.   But again, this should be done with a well structured expression to handle various possible scenarios.

Bottom line, if you want to be able to manipulate the MODE from the Operator station, you cannot wire the MODE parameter, as the wired value will always overwrite the target value written by the operator.

Andre Dicaire

Many reasons NOT to do it this way, but you can.

Below is a DI triggering a mode change between CAS and AUTO.