1.3 Circuit and System Representation - Behavioural, Structural and Physical Representation

A complex digital system is broken down into component gates and memory elements by splitting the system in a hierarchical manner. A set of requirements is envisaged. Guided by these, an initial design is developed and subsequently tested against the requirements. Design has to be improved in case the requirements are not met. The Y-chart (first conceived by D. Gajski) shown in Figure 1.11 demonstrates a simplified design flow that is adopted for the majority of logic chips, using the activities on three different axes (domains) which resemble the letter "Y".

The three domains of representation that make up the Y-chart are the behavioural domain, the structural domain and the physical layout domain. The behavioural view of a digital system describes its function of the system with no regard to its implementation. The structural view of a system describes a system as an interconnection of components. The physical view of a system is concerned with the physical entities, namely the transistors that constitute the circuit.