adccommunitymod (AutomationDirect) asked a question.
Created Date: October 21,2010
Created By: clintonp
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Is there something special about memory locations V400-V677 in a DL06? I use some of these locations as my MODBUS RTU output registers. I'm adding a bit to a register, and I want the SCADA system to be able to reset the bit. Doing some initial testing, I was looking at the bit (B634.15) with DS5 ( 'Change Value ' pop-up). When I look at the bit, a message appears at the bottom of the Change Value pop-up box: "Element is read only! ", and the WRITE PLC button is grayed out. I then looked at the data as a word -- V634 -- and I would SWEAR that the WRITE PLC button was grayed out. But now when I look at it, as a word, I can read it and write it (as a word). Now I 've scouted around a little bit, and the "Element is read only! " message appears whenever I look at a specific bit. So it looks as though it's a feature. Anybody understand this behavior? Perplexed (again!), Paul in WI
Created Date: October 21,2010
Created by: bcarlton
Even in Directsoft you can't affect just a single bit in the normal V registers. The bit type registers (C for example) can be changed individually.
Created Date: October 21,2010
Created by: Do-more PE
Bernie is correct. To check this out, try putting B2000.0 into the box. You will get the same message.
Created Date: October 21,2010
Created by: clintonp
Thanks re: setting bits from DS5
Thanks for the responses. I was afraid that somehow these bits were 'protected ' or read-only from the outside world...
Paul in WI
Created Date: October 22,2010
Created by: franji1
The actual situation is that you cannot write to bit-of-word. DirectSOFT interprets "readonly " and "cannot write " as meaning the same thing, but actually they are not.
Believe it or not, the serial protocol you select can affect this functionality for even C bits. DirectNET does not support writing to single bits. It's always best to use K-Sequence when using DirectSOFT on a Serial port. For Ethernet, choose ECOM protocol, which actually intelligently chooses between DirectNET or K-Sequence application layer request across UDP to do the "best " or "optimal " request on a request-by-request basis.
Created Date: October 21,2010
Created by: clintonp
Is there something special about memory locations V400-V677 in a DL06?
I use some of these locations as my MODBUS RTU output registers. I'm adding a bit to a register, and I want the SCADA system to be able to reset the bit.
Doing some initial testing, I was looking at the bit (B634.15) with DS5 ( 'Change Value ' pop-up). When I look at the bit, a message appears at the bottom of the Change Value pop-up box: "Element is read only! ", and the WRITE PLC button is grayed out. I then looked at the data as a word -- V634 -- and I would SWEAR that the WRITE PLC button was grayed out. But now when I look at it, as a word, I can read it and write it (as a word).
Now I 've scouted around a little bit, and the "Element is read only! " message appears whenever I look at a specific bit. So it looks as though it's a feature. Anybody understand this behavior?
Perplexed (again!),
Paul in WI