The introduction of the bicausality concept in the bond graph language has allowed new analytical methodologies of a system, for instance in the context of model inversion, mechatronic system sizing and control. The causality assignment generally imposes the way these constitutive relations have to be used. In the case of linear multi-port elements, derivative causality or of bicausality is not necessarily possible. The conditions for the existence of a causal configuration are related to the form of the constitutive relation of the multi-port element. In this paper, we propose to inspect this condition and then to focus on the use of the causality applied to the linear multi-port elements. We show that the constitutive relations of any linear multi-port element may be used to determine quickly what kind of causality assignment does exist and what could be determined using different schemes of calculus. It clearly appears that this approach may be applied in other contexts and may have interesting applications on system sizing, identification and control.