Usage Of DPE attributes by API manager

When API manager is configured as a DIP client

User bits

The first 2 user bits are used to hold the quality of the data being written into the DPE. OPC quality mappings used as basis for this policy.

DIP Quality WinCC OA users bits
DIP_QUALITY_UNINITIALIZED (-1) 0 decimal (00 binary) = bad
DIP_QUALITY_BAD (0) 0 decimal (00 binary) = bad
DIP_QUALITY_GOOD (1) 3 decimal (11 binary) = good
DIP_QUALITY_UNCERTAIN (2) 1 decimal (01 binary) = uncertain

Note the reasonForQuality string (which provides supplementary information on the quality when it is not good) is not used by the API manager.

Use of invalid flag

The DPE invalid flag is used to indicate either either a problem in the API manager or the DIP publication does not exist.
  1. The API manager can not find a converter to convert from the DIP to WinCC OA type.
  2. The publication the DPE is associated with is not available.
  3. If a type conversion has failed (i.e. The data type of the publication has changed).

If the invalid flag is set then the value and user bits are NOT to be trusted.

Timestamp

The timestamp supplied with the received DIP data is used as the timestamp for the DPE value.

 

Client Scenarios

Below are a list of scenarios that you may expect to encounter in a running system and an indication of how the API manager will behave in that scenario.

  1. API manager subscribes to publication that does not exist. What to expect:- Invalid bit will be set to true (time stamp will be 0), value & user bits will be left unchanged.
  2. Publication is created (but not published data) AFTER the API manager subscribes.  What to expect:- Invalid bit will be set to false, user bits will be set to bad (time stamp will be 0) & value will be left unchanged.
  3. Publication publishes data AFTER API manager subscribes. What to expect:- Invalid bit will be set to false, value & timestamp set from DIP  value/timestamp. User bits will be  set from the DIP quality according to the mapping described above.
  4. API manager subscribes to publication that exists but has not sent data. What to expect:- Scenario 1) followed be 2)
  5. API manager subscribes to publication that exists and has sent data. What to expect:- Scenario 1) followed be 2), then 3)
  6. API manager subscribes to publication that disappears. What to expect:- Invalid bit will be set to true (time stamp set to current time), value & user bits will be left unchanged.
  7. API manager subscribes to publication that changes its data type.  What to expect:- As scenario 6).

 

 

 

 

When API manager is configured as a DIP Publisher

Use of invalid flag

If the invalid flag is set for any DPE used to make up the DIP publication then the quality of that publication is set to bad. The reason for quality string indicates how many DPE's for that publication have their invalid bit set.

Timestamp

Of all DPE's that make of the publication, the one with the most recent timestamp is the one which provides the time stamp for the data sent via the DIP publication.