Causality Condition of a Discrete-Time LTI System As xi[n]+x2[n] for n>no the only way the condition ∑ h(k]xno k]=∑k]x2{-h k=-0o k=-0o will hold if both sums are equal to zero, Which is satisfied if h[k]=o for k<0 Copyright C 2001, S.K. MitraCopyright © 2001, S. K. Mitra 9 Causality Condition of a Discrete-Time LTI System • As for the only way the condition will hold if both sums are equal to zero, which is satisfied if x [n] x [n] 1  2 n  no   − =− − =− − = − 1 2 1 1 k o k o h[k]x [n k] h[k]x [n k] h[k] = 0 for k < 0