SUBX
Subtracts one hexadecimal number from another.
Command Class
TCL-I command.
Syntax
SUBX m s
Syntax Elements
m is a hexadecimal number (minuend).
s is a hexadecimal number (subtrahend).
Negative Numbers
Hexadecimal numbers are considered negative when in the range from 
X'FFFFFFFFFFFF' (-1) to X'800000000001' 
Example
:SUBX FF AE
      51