Hi all,
Just consulted both sets of FCOM. BOTH 340 and 320 require's "on ground" sensing from at least one(of two) LGCIU (Landing Gear Control and Interface Unit) in conjunction with other selection inputs to allow reversers to deploy. Only reverse idle is available until all four blocker doors are fully open. Also on the 340 engines 1 & 4 have an interlock that prevents asymmetrical reverse thrust.
Hope this helps you all
Have a nice day