Writing over consumed tags

Hi,

Say I produce in PLC-A data A and consume data A in PLC-B and PLC-C. PLC-B and PLC-C can write to the consumed tag, but if they do, does PLC-A see it?

Overall my question is, are produced/consumed tags one directional?

Thank you,

Josh

No. The produced tag will overwrite it. Producer/Consumer is unidirectional. Producer --> Consumer. If you want data to go back to the "Producer" PLC, you will need to setup another Produce/Consumer connection, this time with the "Producer" PLC being the consumer.

Great, so I do not have to guard the data then. Just wanted to make sure. Thanks!

JoshM said:

PLC-B and PLC-C can write to the consumed tag

Josh

Click to expand...

Just to clarify, if you overwrite the comsumed tag, it will be overwritten again by the produced tag at the RPI interval.

JoshM,

Hold on a second! If i understand your question correctly, PLC A writes data to PLC B & C. You also want PLC B&C to write data to the same addresses. if this is true, then you should be aware thet PLC A can write the data to PLC B & C at any time, even in the beginning, 1/3 way, middle, 3/4 into the program or at the end of the scan. the data from PLC B&C could be over written and be lost.

I strongly advise against having PLC B & C write data into registers that PLC A uses. You cannot predict what data you are using.

Not trying to slam you, i had this happen several years ago and they didn't realize for several weeks what was happening.

regards,
james

Why don´t you create another tag and move data from consumed tag whenever you desired or get data from another source. Normally produced-consumed scheme is left the way it is i.e. updated from produced to consumed tag.

You guys are correct. I do not plan on doing this, but was curious how scan time and produced/consumed timing play out. So produced/consumed tags are independent of the PLC scan time throughout the code?