Mapping CygNet Point States to OPC Quality and Sub-Status

The CygNet OPC Servers provide a sophisticated method for mapping "point state" to OPC quality and sub-status values. The CygNet CvsMetadata XML file provides default mappings from the defined "point states" and "point state instances" for Point Scheme 0 to the OPC quality and sub-status values as follows.

CygNet Scheme 0 Point State	Quality and Sub-status Bytes
NORMAL	Hex 0xC0, decimal 192, OPC Quality = "Good"
UNRELIABLE	Hex 0x44, decimal 68, OPC Quality = "Uncertain", Sub-status = "Last Usable Value"
UNINITIALIZED	Hex 0x08, decimal 8, OPC Quality = "Bad", Sub-status = "Not Connected"

Note: When data is retrieved from the CygNet OPC HDA server the OPC quality property is also returned, appended with a sub-status of OPCHDA_RAW (if timestamp is exact) or OPCHDA_INTERPOLATED (if timestamp is interpolated).

See Mapping CygNet Point States to OPC UA Status Codes for more information about how this is handled in the CygNet OPC UA Server.

CVS Metadata Mapping

Point Scheme definitions can be modified to customize the mapping of the user-defined "point states" and "point state instances" to the desired OPC quality and sub-status values. The CygNet OPC Servers load the CVS Metadata XML and resolve the appropriate OPC quality and sub-status values based on the highest precedence "point state."

See the following CvsMetadata elements in the Points section of the CygNet Help for more information:

PointStateDefinition attribute: ext_status
PointStateInstanceDefinition attribute: ovrext_status

The CygNet OPC Servers will also set the OPC quality and sub-status values, regardless of resolved point state, based on the following conditions.

OPC Server	Quality and Sub-status Byte
Unknown tag	Hex 0x01, decimal 1, OPC Quality = "Bad", Sub-status = "Configuration error"
Unknown Point Scheme	Hex 0x01, decimal 1, OPC Quality = "Bad", Sub-status = "Configuration error"
Failed to connect to CygNet	Hex 0x18, decimal 24, OPC Quality = "Bad", Sub-status = "Comm. Failure"
CygNet message response error	Hex 0x18, decimal 24, OPC Quality = "Bad", Sub-status = "Comm. Failure"

If the CygNet CVS Metadata XML file fails to load when the CygNet OPC Server starts the following will occur:

A warning is added to the log file and displayed on the status bar of the CygNet OPC Server dialog box.
The CygNet OPC Server will continue to try to load the CVS Metadata until the metadata no longer fails to load.
The CygNet OPC Server will revert back to the old OPC server behavior, described below:

OPC Server	Quality and Sub-status Byte
Success	Hex 0xC0, decimal 192, OPC Quality = "Good"
Unknown tag	Hex 0x01, decimal 1, OPC Quality = "Bad", Sub-status = "Configuration error"
Failed to connect to CygNet	Hex 0x18, decimal 24, OPC Quality = "Bad", Sub-status = "Comm. Failure"
CygNet message response error	Hex 0x18, decimal 24, OPC Quality = "Bad", Sub-status = "Comm. Failure"

On Success the OPC servers will return "Good" instead of mapping the point state to an OPC quality and sub-status value.