User manual

Computer Gateway User Manual 4-38 5/96
4.5
4.5 INTERNAL DDT PREPARATION MESSAGES
The messages in this section are a necessary precursor of any table-driven get and store
requests. They are concerned with the establishment and saving of point-identifier tables
required by the table-driven request messages.
4.5.1 Build Internal DDT Request
The host processor sends this request to initiate the external-to-internal identifier
conversions for a specified table of point.parameters.
Eight-Character Tagname Form
Header information: Word 1—Transaction Code = 6
Word 2—Number of Words = 9 + total for external
name/parameter sets (10 words each)
Word 5—CG Identifier = 2
Message format: Word 1—table purpose (integer) 1=input table
2=output table
5=history query table
Words 2..5—order of data types in table (integer)
0=no entries
1=real
2=integer
3=ASCII (24-character string)
4=enumeration
*
(ASCII string)
OR
5=enumeration (ordinal value)
13=internal entity id
15=external entity id (ASCII name)**
17=LCN internal time
19=ASCII (40-character string)
These ordering values can be assigned in any sequence; however,
none of the data types can be repeated, and you cannot have both
enumeration and ordinal types in the same DDT.
Words 6..9—number of points of each type (integer array)
These values must be presented in the same order as in words 2
through 5.
Word 10—start of 10-word external name/parameter sets
Name/param set format: Words 1..4—point name (8 ASCII characters)
Word 5—point name index (integer)
Words 6..9—parameter name (ASCII characters)
Word 10—parameter index (integer)
Use information: Same as for the sixteen-character tagname form explained below.
___________________________
*
See Paragraph 4.6.4 for restrictions on the use of Enumeration values in Store Data requests.
**Store (output) of external entity id (ASCII name) is not permitted.