Data type determination

When a client sends a read/write request to the ABCIP Communication Driver, the server needs to know if the tag is defined in the controller; it also needs to know the tag’s data type and size. To determine this information, the ABCIP Communication Driver internally builds the item table (tag database) in the server-specific code before any item is created.

• This table includes information on the item's name, data type, and size.

• If an item is a structure, it also includes its members and their data types.

To build the table, the ABCIP Communication Driver sends a request to the controller for all the tag information defined in the controller. The controller then returns all the information needed. The table is built one time for each controller, unless a "refresh" request is received from the client. The ABCIP Communication Driver does not rely on the Allen-Bradley .csv and .L5K files.

Important: The manual "refresh" tag database request for the Logix processor needs to be activated by your writing "true" (of type VT_BOOL) to the $Sys$UpdateTagInfo; it is not activated by selecting the option (check box) as was implemented in the ABCIP OI Server 1.1.