ModBMS Prevents OPC Client from Writing OPC DA Values to Sigma

[Product_Support]

Issue

ModBMS does not allow an OPC Client to write OPC DA values to Sigma. However, reading values from ModBMS/Sigma is successful.

Product Line

Satchwell BAS & Sigma

Environment

• Sigma versions 4.04 and earlier
• ModBMS
• OPC Client

Cause

ModBMS uses DDE (Dynamic Data Exchange) functions to read and write data to the Sigma server.
In Sigma versions prior to 4.05, the DDE write function was not supported. This limitation was resolved in Sigma version 4.05 and later.

Resolution

To enable OPC DA write functionality, upgrade Sigma to version 4.05 or later, where the DDE write capability has been implemented.