levelsynchronous

Levelsynchronous is a term used in digital design to describe circuits whose state changes are governed by the level of the clock signal rather than by clock edges. In a level-synchronous design, storage elements are often level-sensitive latches that are transparent when the clock is at a particular level (typically high) and become opaque when the clock switches to the opposite level. This contrasts with edge-synchronous designs that sample inputs only at clock transitions using edge-triggered flip-flops.

Operation in level-synchronous designs relies on latches that propagate data while the clock is in the transparent phase and hold data when the clock is closed. Data paths must settle within a clock phase, and hold times must be respected to avoid hazards. Designers must manage clock skew and ensure that data does not propagate into a latch when it is supposed to be closed. The timing model is therefore tied to clock level behavior rather than a single edge.

Advantages and considerations include simpler implementation with latch-based structures and potential for flexible timing in short pipeline stages. However, level-sensitive designs can be more susceptible to glitches and race conditions if inputs change while a latch is transparent. Compared with edge-triggered designs, level-synchronous pipelines may require careful clock-phase control and sometimes additional latching to prevent data from racing through multiple stages within one clock interval.

See also: Level-sensitive latch; Latch; Edge-triggered flip-flop; Micropipeline; Clocking in digital circuits.