Input isolation for self-resetting cmos macros

Abstract

Very fast very large scale integrated (VLSI) chips can be built-up from 'self-resetting' or 'self-timed' macros. An input isolator circuit provides an effective input isolation/decoupling which allows the input pulse widths to vary over a wide range. This avoids, for a large chip having many macros, a significant problem in insuring that the output from one macro is compliant with the input requirements of a receiving macro. Mixed static and dynamic circuits are used. The circuit comprises three stages. The input first stage is a static NOR circuit providing a pulse-chopping function. This first stage chops any too wide input pulse to the desired pulse width. The middle stage is a self-resetting complementary metal oxide semiconductor (SRCMOS) dynamic NOR circuit to capture input which is reset too soon. The last stage is a half-latch circuit to keep the dynamic node at constant output voltage level. The interfaces of all self-resetting macros in accordance with the teachings of the invention have no need for a handshake circuit or interlock circuits.