ABSTRACT
Prevailing synchronous digital ICs use clocks to synchronize and coordinate the operations of circuit components. While the clocked control mechanism is efficient and simplifies circuit design, it also limits the flexibility and reliability of synchronous circuits. Asynchronous logic circuits, on the other hand, do not utilize a clock for synchronization; instead, handshaking protocols are used to communicate between circuit components and control their operations. NULL Convention Logic (NCL) is delay-insensitive, which means that NCL circuits will operate correctly regardless of when circuit inputs become available; therefore NCL circuits are said to be correct-by-construction. In order to be pin-to-pin compatible with commercial synchronous counterparts, the NCL 8031 microcontroller follows the same architecture. Clock-controlled synchronous circuits are highly sensitive to speed changes and are therefore very difficult to reach timing closure during temperature swings. Delay-insensitive asynchronous circuits such as NCL, which use handshaking protocols in lieu of clocks to coordinate and communicate between circuit units, are correct-by-construction.
