HP E4418B Programming Manual page 460

Query
*DDT?
The query returns the action which is performed on receipt of a GET or
*TRG. This is returned as a <definite length arbitrary block response
data> value which is in the form of #nN<action> as described on
page 15-8.
Error Message
If an invalid parameter is received error -224, "Illegal parameter value"
occurs.
HP E4418B/E4419B Programming Guide
*DDT <arbitrary block program data>|<string program data>
IEEE488.2 Command Reference
15-9