Siemens HMI can't see db values

nerdfactormax

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Join Date
Feb 2008
Location
Adelaide
Posts
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I have a MP277 connected to an 317T.
M bits and MD values work fine, but db bits and words don't work.
I've checked and double checked the addresses but I can't get any values that I enter on the HMI to appear in the db. (or vice versa)
 
Is the panel online ? Do you get the message "connection established" at startup ?
Are there values, or just zeroes, or "####" in the numerical io fields on the panel ?
You can see the online values from the DBs in a VAT in STEP7 ?
If yes, can you set values via the VAT table, and the set values remain ?
If yes, try to start the WinCC Flex RT from your PC. Does it go online OK ?
If yes, try to set values from the RT on your PC.
Check that you havent inadvertently created multiple connections in the WinCC Flex project (can happen when you copy back and forth between projects).
 
Last edited:
The values are 0 after the HMI project is downloaded. The values in the db are nonzero.
I can enter values into the numerical entry boxes and they stay there, but they are not reflected in the db and they are not retained after HMI project download.
I can modify the db values from within the ladder view online and the values remain.
Only one connection in the HMI project. My buttons connected to M bits work fine and I have a MD numerical entry and that works fine, too.
 
This is quite odd. I cant see anything wrong.

Only thing is that you have all update rates at 100 ms. I would reserve that to the few tags that actually require such an update rate. But I cant see if that should mean that the values do not get transferred.
*: Since you are online via DP, I would definitely limit the update rate to generally 1 sec, and only 200-500 ms for the tags that REALLY require it.

Try to rebuild all. And do the test again.

The relevant fields on the panel are input/output fields ?
 
Last edited:
I'm connecting via Ethernet with few tags on screen at once. Last machine had many more tags at 100ms with no issue.
There are no other PLC's or simulators, so no possibility of connection confusion. Tried rebuild all (again) to no avail.
All fields are input/output by default. I even copied the working field and changed the address.
If I disconnect the PLC the values stay as they are. If I reboot the screen with the PLC disconnected, all values are 0. When I reconnect, the invalid address reads #####, the M address updates with the correct value and the DB address stays as 0.
 
It is a 317T-2DP, so the ethernet is via a CP343-1, right ?
All the data has to pass through the very slow MPI backplane bus at 187.5 kbps.

I suggest to post your project where we can upload to check it. Or send me a PM.
 

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