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Data Table Index...time needed to write and read a row?


ORSO2001

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Dear All,

 

I tried to use the Data Table Index; I created a Struct with 2 columns...a number INT16  and a name STRING with lenght 10...I put online the PC with the PLC to check the data table refresh and I see that to transfer the values into the data table is needed 10 or more seconds...same thing to write a row already inserted. Some suggestions?

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Hello,

 

I don't know if I properly understand what the issue is.

 

It takes 10 seconds for the data table in the PLC to update in UniLogic while online with the PC?  Are you directly connected to the PLC?  Does the data table data update instantly on the PLC, or does it also take a long time?

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Dear Pratt,

 

sorry for delay answer...yes the PC was directly connected with the PLC by usb cable...yes both transitions (read from and write to DTI) needed 10 sec...but I want update the situation...I have replaced the SD card that I used with a new one (I bought it yesterday...for this reason I write only now) and now all works properly...the function is the same I don't modified nothing...I tried it because after that I have checked how the transfer of DTI to SD works I have found that the SD was not recognized!...is possible that a fault SD can be the cause of it! I don't came back in the original situation to test maybe I will try it next days.

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Thank you for the update!

 

Yes, a faulty SD card would be the cause of delayed read and writes to the DT.  We can verify if the PLC recognizes the SD card and if there are any faults through the status integer in the DTI struct and through the system struct, 'External Storage'  and 'SD Files'.

 

If you would like a further review, please send your program in to support@unitronics.com with the brand and capacity of the faulty SD Card used.  Also, if you can verify any faults with teh faulty SD card when trying to read or write to the DT, please let us know of these too.

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Hi, write row and read row are instant, since the table is located in RAM of the CPU and it is all done in ladder.

The only things that takes time is Saving the DTI to a file or loading it from a file, since this requires accessing the Panel (where the SD is located), and furthermore, file system operations takes a long time (You can see it in your computer, when you copy a file).

 

The 10 seconds delay might be related to the Online (It somehow got a delay, which is maybe related to the faulty SD Card), but that doesn't mean that it took 10 seconds to read or write a row to the DTI, since it involves only RAM operations of the CPU.

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Dears Pratt and Saragni,

 

Yesterdy I was stesting some modification (I have created a new DTI) of my program, the PC and PLC was connected together by a USB cable,..the SD card is the new one (32 GB , mSDHC)...now I have that the PLC update the tag's value immediatelly when it try to read an existing row...the update of the DTI grid on the PC needed a very long time and for 2 times the PC interrupted the connection with the PLC with an alarm windows and the PLC crash and reboot itself...? after the second crash the situation is back "normal" (no crash). 

today I will send you my program to check it and the old SD data. thanks in advance

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