Strange values

[Bryll 31]

I have a project with a 317F CPU (Program made in Step 7 Classic) and a TP1500 Comfort (Made in TIA Portal V11) communicating on the MPI bus. I'm reading two analog values that I scale to show an airflow value between 0 to 80 000 m3/h (DINT). The PLC shows the correct decimal values up to 80 000 when monitoring online. But, when I try to display it in the terminal as a bargraph and a decimal value is the highest value 65 534 (2 x 32 767) and for values over that starts from zero and counts up. Everything is declared as DINT, but the panel is displaying as if it was an UINT. I've checked for errors made by me all over the project, but I cant find anything. Any good ideas ?

[Bryll 31]

Some more info regarding the problem. In the PLC is two DINT declared (MD26 and MD30) and transferred to the HMI. The HMI has two bargraphs and two decimal value fields for the two DINT's The tag list in the PLC and the one in the HMI are identical, I double checked this a couple of times. Now to the strange thing. One is correct and the other one is corrupt. The corrupt one starts over from zero if the value goes over 65 534. Everything is compiled and transferred to the HMI and PLC several times without any correction of the behaviour. This is such a simple thing so it should work right away. Anyone with a good idea where the problem is ?

[drx 2]

Hi, Well, if one is correct and not the other, my guess is the wrong value is corrupted somewhere in your program ie MB27 or MW28 could be used in another routine. I'm afraid you don't have much choice but try to cross-ref all the possible components of your DINT, including possible MW/MD on the previous bytes... MW25 could corrupt MD26, so would MD23,24,25... Could also be a problem with the endianess, but you would have it on both values... If you wanna be sure to avoid such a corruption, you oughta think about using a DB to strore those values and see if it gets better. Good luck. Edited 6 Feb 2014 by drx

[Homer_BL 2]

Maybe on TP1500, for tags, to choose acquistion mode "continous", not "in operation" (default) for both tags. Edited 19 Feb 2014 by Homer_BL

[Bryll 31]

They are set to "Continous" already. A guy told me to remove the tags, compile, and then create them again and recompile. It helped him a couple of times when he got similar problems

[Homer_BL 2]

Ugh... Works now, after that?