A Level-Encoded Transition Signaling Protocol for High-Throughput Asynchronous Global Communication

A new delay-insensitive data encoding scheme for global communication, level-encoded transition signaling (LETS), is introduced. LETS is a generalization of level-encoded dual rail (LEDR), an earlier non-return-to-zero encoding scheme where one of two wires changes value per data bit per transaction. In LETS, only one of N = 2ⁿ (1-of-N) wire changes value per n data bits per transaction. Compared to most common return-to-zero encoding schemes, LETS has potential power and throughput advantages, since fewer rails switch and no return-to-zero phase is required. Compared to existing nonreturn-to-zero schemes (i.e., LEDR), higher-dimension LETS codes have a potential power advantage, with significantly reduced switching activity per data bit.Two alternative 1-of-4 LETS codes are proposed, and efficient hardware for completion detection and conversion to return-to-zero protocols is introduced. Finally, a general theoretical framework is presented which characterizes the properties of arbitrary 1-of-N LETS codes, as well as a simple procedure to generate such codes.