As I view it, when it operates, autotrim obeys the pitch-orders from sidestick or AP by following the elevator. If the order is nose-up, THS trims nose-up. If the order is nose-down, THS trims nose-down.
Just for information...
Under many conditions, there are times in both Alternate and Normal laws when the auto-trim will briefly operate
opposite the pilot SS input when the SS input causes the aircraft to experience "G" noticeably above or below 1 "G" as displayed in amber on the lower display.
The same thing occurs in terms of elevator surfaces movement (SD F/CTL page) if the manual trim wheel is rolled briskly in one direction or the other with hands off the SS, i.e. the elevator will briefly deflect opposite during the manual trim wheel input.