User manual

Computer Gateway User Manual 4-93 5/96
4.8
4.8 HISTORY DATA TRANSFERS
History data requests are limited to the data types that can be historized. These are
primarily analog points with parameters that are expressed as real values; however, history
snapshots can include digital points that are expressed as integer (ordinal) values.
Up-to-four concurrent History requests (from separate ACPs) can be accepted by the CG.
A fifth request will be rejected with a queue-full return status.
4.8.1 Get History Request
This message is sent by the host processor to request the transmission of previously
historized data from the HM.
Eight-Character Tagname Form
Header information: Word 1—Transaction Code = 50
Word 2—Number of Words = 30 plus size of the Internal DDT
table
Word 5—CG Identifier = 2
Message format: Words 1..4—ACIDP name or blank (8 ASCII characters)
Word 5—history type (integer)
0=snapshots at 60-second interval
1=hourly averages
2=shift averages
3=daily averages
4=monthly averages
5=user averages
6=reserved for future use
7=monthly averages at fast interval
8=sampling rate enquiry
9=snapshots at 5-second interval
10=snapshots at 10-second interval
11=snapshots at 20-second interval
Word 6—history mode (integer) 0=absolute
1=relative
Words 7..17—beginning date and time (22 ASCII characters)
Words 18..28—ending date and time (22 ASCII characters)
Word 29—beginning offset (integer)
Word 30—ending offset (integer)
Word 31—start of Internal Data Table
Use information: Same as for the sixteen-character tagname form explained below.