GPRS & SMS conflicts

[ahoover]

Hi,

My goal is to administrate( online test, download updated programs ) on Vision series PLC's, remotely. I have been trying to do this using GPRS, but have run into some problems. Can anybody help me out?

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Here is the hardware I'm using:

* Enfora Modem with ATT card (card is assigned a private IP) on PLC

* Vision V570 PLC

* PC running Visilogic 9.4.0

* DSL router with port forwarding to my PC

This is process I have been trying:

* Send SMS with IP address of DSL router

* Initiate a GPRS call, either with button on screen, or with SMS message

And here are my experiences:

* When initiating a "call" from the screen, I don't have a problem connecting to Visilogic. The problem seems to be conflicts between SMS & GPRS. When a GPRS call has been made,

and ended, the PLC will not receive any SMS messages, until the PLC has been rebooted. When an SMS message has been recieved (before any calls are made), then a

call is started, the PLC will crash with this message: Illegal Word Operand Access.

* The above seems to happen consistently, although it may be a problem in my program ( see attached file ). If I use the above method to remotely administrate PLC's, I most certainly

need a method of "calling from the PLC" remotely.

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My next question: Is the above method recommended for remote administration, or is there a better way? When I have successfully connected via GPRS the connection seems

very slow, and at least once a download error occurred.