Journal ArticleModular Hardware Design with Timeline TypesNigam, Rachit; Azevedo de Amorim, Pedro Henrique; Sampson, AdrianModular design is a key challenge for enabling large-scale reuse of hardware modules. Unlike software, however, hardware designs correspond to physical circuits and inherit constraints from them. Timing constraints—which cycle a signal arrives, when an input is read—and structural constraints—how often a multiplier accepts new inputs—are fundamental to hardware interfaces. Existing hardware design languages do not provide a way to encode these constraints; a user must read documentation, build scripts, or in the worst case, a module’s implementation to understand how to use it. We present Filament, a language for modular hardware design that supports the specification and enforcement of timing and structural constraints for statically scheduled pipelines. Filament uses timeline types , which describe the intervals of clock-cycle time when a given signal is available or required. Filament enables safe composition of hardware modules, ensures that the resulting designs are correctly pipelined, and predictably lowers them to efficient hardware.2023-06-0610426595Proceedings of the ACM on Programming Languages7PLDI343 to 3672475-1421https://doi.org/10.1145/35912341845952; 2124045; 1909073National Science Foundation