I have a WonderWare application at my main site that I need to have communicate with a SLC-5/04 at a remote site via a modem. I am using the ABKF2 I/O server. I dial up the modem and use the escape code (+++) to release control of the modem and then start the ABKF2 server. The ABKF2 server won't take over the modem because it says the modem isn't free. Does anyone have any other suggestions?

 

Maybe there is need for an intermediate device to handle the handshaking between the modems(RTS signal hardware handshaking/flow control), something like Black Box.
Also you may want to try changing the default protocol setting of the I/O server is DF1 (Full duplex) to Master/Slave.

Or better yet try Software Toolbox for there Allen-Bradley DF1 Serial FastDDE/Suitelink/OPC Server with NT Service AND MODEM Support: Uses FastDDE that will provide you a set of pre-configured tag names that you write to for setting up of dialup modem connections and triggering the dialing.

 

2 questions for you:
- What operating system is on the workstation?
- What are you using to dial up the modem (e.g. Terminal, Hyperterminal, etc)?

If it is Win98, there should be a setting for the COM port to allow sharing. If it is WinNT/2000, the OS does not allow the COM port to be shared. Instead of using +++, you will probably have to shut down the software which does the dialing, usually which drops the connection. However, there are ways around this, as long as you are using an external modem.

1) Using Terminal/Hyperterminal, add &D0 to the modem initialization string. This tells the modem to ignore the DTR signal.
2) Dial up as usual to the remote device.
3) Close Terminal/Hyperterminal. If it asks if you want to hang up the connection, choose No. Closing the program would normally hang up the software, but the &D0 in the init string lets the modem ignore that.
4) Now start up the ABKF2 driver. Since Terminal/Hyperterminal is no longer running, there should be no problem grabbing the COM port.
5) Remember that the modem will now remain connected even once all software is shut down. To disconnect, re-open Terminal/Hyperterminal, and enter +++ then ATH0 (or simply power down the modem, which is another reason for using an external).

I have used this regularly with Modicon and GE devices, there is no reason it should not work with AB's driver.

Regards,
Don Zunti, P.Eng.
Delco Automation Canada