STX - Store Index Register in Memory ;flags(N,Z)
STX opr ;(opr) <= X ;(DIR) 8 bit direct
STX opr ;(opr) <= X ;(EXT) 16 bit extended
STX ,X ;(X) <= X ;(IX) indexed no offset
STX opr,X ;(opr+X) <= X ;(IX1) indexed w/8 bit offset
STX opr,X ;(opr+X) <= X ;(IX2) indexed w/16 bit offset
The contents of X remain unchanged.