1. A method of monitoring operation of a memory system that is operable in response to control signals received from a processing unit, the method comprising the steps of: producing first and second digital state signals, each being respectively associated with the processing unit and the memory system, and each being indicative of the (1) control signals produced by the processing unit and received by the memory system and (2) prior produced digital state signals; and comparing the first and second digital state signals to produce therefrom an error signal indicative of improper operation.