Only One DDE Device Per IOGroup?

[josborne]

Hi. Its me again.

I am not sure if the following case is the way DSC i intended to function, but here is my problem:

I have a simple DSC setup with two DDE tags (download the SCF file below). The tags point to two DDE Servers on two separate remote machines. It appears as though DSC does not allow you to put these two tags in the same IOGroup. Technically you can do it, but the Tag Configuration Editor will always change your tags to force them onto the same DDE Device. Here's my example:

Tag Name ServerName IOGroup Device Item

DDETag1 DDE Server Imatis \\johno\NDDE$|MyExcel1$ r1c1
DDETag2 DDE Server Imatis \\platform1\NDDE$|MyExcel$
r1c1

I have specified two separate devices for the IOGroup. That works OK. But if you change the device for one of the tags, the other tag is automatically changed to have the same device.

Download the SCF file below to see this in action:

1. Open the SCF file
2. Double-click on each of the tags to see what device they are connect to (\\johno\NDDE$|MyExcel1$)
3. Change one of the tags to the other DDE Server (\\platform1\NDDE$|MyExcel$)
4. Aftwerwards, You will notice that the other tag is automatically changed to that device, too

Is this the intended function? Can we only have one DDE Server per IOGroup? If we can only have ONE DEVICE per IOGROUP, then why is it possible to add devices to the IOGroup?

I haven't reported this to NI Tech support yet because we have an obvious workaround (put all DDE Servers in separate IOGroups)... also, I am guessing that this is the way DSC is intended to function. I'm also curious if the same thing happens with OPC Servers.

[AAD]

John Paul

Unfortunately this is the intended function. You can only have 1 device per I/O group. The workaround that you have discovered is the way that you are intended to bring in 2 seperate Servers.