HP 16554A Programmer's Manual page 133

Query :MACHine{1|2}:SLISt:XTAG?
The XTAG query returns the X marker position in time when time tagging is
on or in states when state tagging is on, regardless of whether the marker
was positioned in time or through a pattern search. If data is not valid tagged
data, the query returns 9.9E37 for time tagging, or returns 2147483647 for
state tagging.
Returned Format
[:MACHine{1|2}:SLISt:XTAG] {<time_value>|<state_value>}<NL>
Example
OUTPUT XXX;":MACHINE1:SLIST:XTAG?"
SLISt Subsystem
XTAG
7–23