Control.com - Nerds in Control

I have some issues on a MOdbus communication between a kepware OPC server conected using Modbus protocol to a MK V Turbine Control System, using a Lantronix RS232 - Ethernet converter. Some times the communication fall for 3 or 4 seconds. According the events list "a 34 pack was sent by slave, instead of a 32 expected pack"

This issue could be only RS 232 comm configuration? or could be the kepware driver?

Any ideas?

MatrikonOPC offers a direct highspeed, reliable connection via ArcNet to MarkV turbine controllers. It uses the PCI ArcNet card or the USB to ArcNet converter from Contemporary Controls.

The server can be downloaded from http://www.matrikonopc.com/opc-drivers/303/base-driver-details.aspx

Hmmm, i posted a response to the yesterday but it seems to not have made it up forum.

The error you are seeing is the driver reporting that the response it sent to the RTU for a block of data returned with 34 bytes rather then the expected 32 bytes. My questions were:

1. Do you ever get good data or do you only get this error? Somtimes noise will cause garbage to be added to the packet. recent versions of the driver allow us to ignore that to some degree.

2. What is the device you are talking to sometimes devices like flow meters will use a variation of the Modbus Protocol that uses a single 16 bit register request format to return a 32 bit register response. It is possible the server is reading into a special register section.

3. Have you contacted Kepware Technical Support about this problem. They can work with you to capture some diagnostics to try identify the problem.

Fred Loveless
Senior Application Engineer
Kepware Technologies
http://www.kepware.com