Internet PLC Forum
General => Technical support => Topic started by: can on November 03, 2011, 02:09:42 AM
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Hi. Can I write to 2 different PLC networked together using RS485 under a same site? Currently dm[1] of plc 2 is being overwritten to dm[1] of plc 1. When I make the command inactive, the dm[1] of plc 1 is correctly written. Any idea why is that so?
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Yes, but the two PLC must have different ID. E.g. PLC 1 can have ID = 01 and PLC 2 can have ID = 02.
You then send hostlink or Modbus commands to the specific PLC ID and it would not affect the other PLC.
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Hi. I've tried it and writing single variables is alright. However, when I'm writing a range of DM to plc 1, it is always overwritten with DM that is supposed to be written to plc 2. When I check plc2, the DM is correct. Any idea why this is so?
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We will give that a try and check the result.
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We have found that there is a bug in the ExcelLink software for reading or writing a range of DM[] variables when multiple PLC IDs are configured for different actions in the same site.
When you define different PLC IDs for each active action that is reading/writing a range of DM[]s in a site, data will only be exchanged between ExcelLink and the PLC defined in the last action in the list of actions. The other PLCs defined for previous actions that are reading/writing a range of DM[] data will exchange the same data as the PLC defined in the last action. Thank you for pointing this out, we have forwarded the information to the software development team.
A workaround solution is to create a duplicate site for each PLC on the RS485 network tied to the same TLServer, instead of defining different PLCs for actions in the same site. Each site should have a different name, but the same local host IP address (127.0.0.1) and the same login information.
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Hi. I have another question. If I want to protect my worksheet or hide my worksheet in Excel, can Excellink be able to modify or update the protected or hidden worksheet? Thank you.
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We are not sure. That is a Microsoft issue. If MS Excel allows DDE client to write to hidden cell then it should be OK. But is MS Excel doesn't allow DDE client to write to hidden cell then there is nothing that ExcelLink can do about it.
So best way is to try it. My feeling is that there is no reason why you can't write to hidden cells. But you may not be able to write to protected cells.
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Hi. So is there any way to write to a protected worksheet from excellink? If I'm developing a HMI for a machine, I will want to hide and protect the worksheet from unauthorised modifications. How can that be done?
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See reply above. As we have said it is a Microsoft issue and there is nothing that ExcelLink can do. ExcelLink only send the instructions to MS Excel via DDE command sets. It is up to MS-Excel to decide if it wants to accept the command or to just ignore it.
Generally if a cell is protected it means it is not to be modified. If it is to be modified then it should not be protected.