The XBee / XBee-PRO 
DD parameter is the 
Device Type Identifier field, which is a proprietary AT parameter used on Digi XBee modules.
DD is a 4-byte hex string, consisting of an upper and lower word, which when put together result in a meaningful designation such as "RS-232 Adapter" or "X8 Gateway".
A list of the various 
DD values which can be set 
can be found here.
The 
DD parameter would normally be configured by connecting directly to the XBee mounted on an XBIB dev board and accessing the module with XCTU, or over-the-air from another XBee module in API mode, or an RF Gateway of the same RF network type.
Last updated: 
Jan 01, 2024