Systems Design

> In large-scale embedded system, the design process includes an element of systems design in which functions are partitioned into software and hardware functions.
> The advantage of implementing functionality in hardware is that a hardware component can deliver much better performance than the equivalent software unit. System bottlenecks can be identified and replaced by hardware components, thus freeing the software engineer from expensive software optimization.
> Providing performance in hardware means that the software design can be structured for adaptability and that performance considerations can take second place.

Parallelism
> A great many software systems, particularly embedded real-time systems, are structured as a set of parallel communicating processes which is an outline design of a simple control system.
> With a fast processor, it may not be necessary to implement an embedded system as a parallel process. A sequential system which uses polling to interrogate and control hardware components may provide adequate performance.
> The advantage of avoiding a parallel systems design is that sequential programs are easier to design, implement, verify and test than parallel systems. Time dependencies between processes are hard to formalize, control and verify.

Note:
> There are some applications, such as vector processing, where a parallel approach is a completely natural one. If n-element vectors have to be processed with the same operation carried out on each element, the natural implementation is for a set of n-processes carrying out the same operation at the same time.

Design Process:
Two-stage activity:
1. Identify the logical design structure, namely the components of a system and their inter-relationships
2. Realize this structure in a form which can be executed. This latter stage is sometimes considered as detailed design and sometimes as programming.