Comments on "Stability and absence of overflow oscillations for 2-D discrete-time systems

In their article Xiao and Hill (see ibid., vol.44, p.2108-10, 1996) show via an example that the conditions of the Theorem 3 in an earlier paper by Tzafestas et al. (1992) may not guarantee stability of 2-D linear systems. The authors incorrectly conclude that the BIBO unstable 2-D linear system may have a stable finite wordlength implementation using saturation arithmetic. The authors comment that this incorrect conclusion is due to an erroneous result in the earlier paper by Tzafestas et al.