Higher-Order Abstraction in Hardware Descriptions with C?aSH

Synchronous hardware can be straight forwardly modelled as a function from input and (current) state to an updated state and output. The CλaSH compiler can translate such a transition function, described in a functional language, to synthesisable VHDL. Taking a hardware-oriented viewpoint, components can then be seen as an instantiation of such a transition function. An abstraction called Arrows is used to directly model components by combining a transition function and its state. The abstraction also provides an uniform interface for composition, without losing the referential transparency offered by a functional description. Furthermore, readability of hardware designs is increased by the use of the γ-syntax, that automatically composes components according to the Arrow interface. The advantages of the Arrow abstraction and the γ-syntax are demonstrated by means of a realistic example circuit consisting of multiple components. This is a significant extension to CλaSH and enables many high level abstractions.