Hi Guys,
First time to the Forum! I'll get straight to my problem.
I'm running RSSql v5 and RSLink Pro. v2.41 on a Windows 2000 server. I also have an Msaccess97 database located on the same server(further known as DBMaster). My transactions are working fine. I created another database (further known as DBSlave)on a network drive(n. The tables of DBSlave are linked tables to DBMaster. I created a form in DBSlave that when opened is suppose to initiate a conversation with RSlink on the server via a topic to display information from a SLC5/05 processor. I'm using the following VBA code to initiate the conversation:

ChannelNum=DDEInitiate("\\(network path to server)\RSLink","Topic")
DataBlk=DDERequest(ChannelNum, "N15:100,L84,C84")

The code in DBSlave will work as long as I'm running it from the server where RSLink is located, but when I try to use another PC on the network that doesn't have RSLink I get an error couldn't open channel!!
Can anyone help????????

 

DDE won't operate across a network. NetDDE will but is unreliable. I have had little success getting more than one or two small chunks of data to transfer reliably with NetDDE.

OPC is another option that may work for you.

It would probably be easier to put the VBcode on your DBmaster. Then you could initiate it perhaps from DBslave.

Thomas

 

You need to check if RSLinx Pro will support remote calls for DDE/OPC connections. For the OPC connections you have to have RSLinx Gateway, but I can't remember if that limitation also exists for DDE.

Darren

 

Use OPC

As suggested, use OPC. You will need RSLinx gateway to talk the PLC's without having a version of RSLinx on the client machine.

If you install RSlinx Pro on every client which needs access, you initiate more connections to the PLC than necessary. which may adversely affect the scan time. If you use gateway, and the software calls for a tag or address from multiple clients, it is delivered from the gateway cache. The gateway handles issues of old data quite well, i.e. knowing when to go back to the PLC for new values.

My question is, if you are using RSSQL, why are you going direct to the PLC for data. I would let the DB do the work.

visit http://www.opcfoundation.org. They use to have a forum, but I believe you need to be a member now to participate.