Direct Implementation of Asynchronous Control Units

• Published in: IEEE transactions on computers Vol. C-31; no. 12; pp. 1133 - 1141
• Main Author: Hollaar
• Format: Journal Article
• Language: English
• Published: IEEE 01-12-1982
• Subjects: "one-hot" state assignment; Asynchronous control; direct mapping algorithms; nonfundamental mode operation; parallel operations; sequencer logical design; signaling protocols
• ISSN: 0018-9340; 1557-9956
• DOI: 10.1109/TC.1982.1675937

The "one-hot" row assignment for asynchronous circuits, in which every row in a flow table has exactly one of the feedback variables that equals the value 1, provides a straightforward method for circuit synthesis. Once a flow table has been constructed, the state equations can be directly written, without requiring any procedure to ensure a race-free assignment. Furthermore, it can implement any arbitrary fundamental mode asynchronous circuit, not depending on a specific signaling protocol for its correct operation. An alternate view of one-hot asynchronous circuits is given, with a simple set-reset flip-flop for each state. Although this may seem excessive compared to implementations with encoded state variables, for many circuits their one-hot implementation is comparable in cost to other asynchronous implementations.