Over the past years, various techniques for the embedding of hardware description languages within general purpose languages have been developed and explored. In particular, numerous HDLs embedded in strongly typed functional languages have been developed and used for different applications. A common trait of most of these languages is that they treat hardware components as functions or relations between the inputs and outputs of the circuit. The alternative view, of viewing the circuits as components which can be instantiated, composed and transformed has been a relatively less well explored area in this context. In this paper we present HeDLa, a component-based hardware description language embedded in Haskell, and show how features such as strong-typing and higher-order functions enable us to design and compose circuits in a safer and more abstract fashion. Furthermore, the component-based approach allows access to circuit structure directly, enabling us to reason about non-functional aspects of the component, such as placement, area and power consumption more easily. Finally, we discuss some initial experiments in multi-level simulation of circuits which enable testing and more effective simulation of large circuits.peer-reviewe
