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-   -   Interview question !!! (http://www.plctalk.net/qanda/showthread.php?t=110811)

mohamed abd el raouf July 15th, 2017 07:13 AM

Interview question !!!
 
i was in an interview and i got this question

what is pointer in S7-300 ?
what is it used for ?
can you do a simple project with it using ladder ?


my expression was :whistle::rolleyes::scratch:

how can u do a number of 20 conveyor start/stop ?
i said i can do it with FC or FB but this will creat a DB for each and then call it in OB1

cardosocea July 15th, 2017 08:33 AM

What is a pointer used for normally? To programmatically loop through data, in this case, it can be DBs, internal memory, peripheral memory, etc... there is also something to say about creating a pointer in Simatic which is anything but easy and I doubt anyone knows this by heart without a sheat sheet.

If the conveyors are controlled each by a separate PLC, you can multicast the command. You can broadcast as well, but it's not as elegant of a solution.

mohamed abd el raouf July 15th, 2017 11:32 AM

Quote:

Originally Posted by cardosocea (Post 744407)
What is a pointer used for normally? To programmatically loop through data, in this case, it can be DBs, internal memory, peripheral memory, etc... there is also something to say about creating a pointer in Simatic which is anything but easy and I doubt anyone knows this by heart without a sheat sheet.

If the conveyors are controlled each by a separate PLC, you can multicast the command. You can broadcast as well, but it's not as elegant of a solution.

i think i didn't get the answer
i can find pointer in FC and FB ( variable table - selection on data type )
and the answer of the conveyor i think my answer was good but he ask the question may be it's related to the pointer :huh:

cardosocea July 16th, 2017 08:21 AM

Perhaps... although I don't think so.


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