Delay independent initialization of sequential circuits

Abstract

We show that a given initialization sequence for a synchronous sequential circuit is not guaranteed to work correctly when arbitrary path delays are present in the circuit. In this paper, we present a novel robust-initialization procedure for sequential circuits. This procedure guarantees the correct initialization of state elements of a sequential circuit regardless of delays in the circuit. Every pattern of the normal initialization sequence is repeatedly clocked in flip-flops, so that excessive delays on combinational paths feeding flip-flops do not prevent the proper initialization. This method guarantees the correct initialization of pipeline circuits. For a general sequential circuit which may have feedbacks, we give a simulation procedure to determine the initial state of the circuit that is guaranteed to be correct for arbitrarily large but bounded delays.<>