OPC Toolbox™ software uses specific quality attributes defined by the OPC Foundation, based on a major quality value, a substatus for that major quality value, and a limit status indicating how the value is limited. This appendix describes the standard quality attributes defined by the OPC Foundation that are used in the toolbox, and describes any special extensions that the toolbox uses.
An OPC quality value is a number ranging from 0 to 65535, made up of four parts. The
high 8 bits of the quality value represent the vendor-specific quality information. The
low 8 bits are arranged as
SSSS represents the quality substatus,
LL represents the limit status.
OPC HDA quality values are layered on top of OPC DA quality values.
The following topics describe the OPC quality values and texts associated with each quality part.