Within the scope of this book, a variety of architectural structures are used to introduce
technical concepts and fundamentals of an embedded system. I also introduce emerging
architectural tools (i.e., reference models) used as the foundation for these architectural structures.
At the highest level, the primary architectural tool used to introduce the major elements
located within an embedded system design is what I will refer to as the Embedded Systems
Model, shown in Figure 1-2.

What the Embedded Systems Model indicates is that all embedded systems share one similarity
at the highest level; that is, they all have at least one layer (hardware) or all layers
(hardware, system software and application software) into which all components fall. The
hardware layer contains all the major physical components located on an embedded board,
whereas the system and application software layers contain all of the software located on and
being processed by the embedded system.
This reference model is essentially a layered (modular) representation of an embedded
systems architecture from which a modular architectural structure can be derived. Regardless
of the differences between the devices shown in Table 1-1, it is possible to understand
the architecture of all of these systems by visualizing and grouping the components within
these devices as layers. While the concept of layering isn’t unique to embedded system
design (architectures are relevant to all computer systems, and an embedded system is a type

of computer system), it is a useful tool in visualizing the possible combinations of hundreds,
if not thousands, of hardware and software components that can be used in designing an
embedded system. In general, I selected this modular representation of embedded systems
architecture as the primary structure for this book for two main reasons:

1. The visual representation of the main elements and their associated functions. The
   layered approach allows readers to visualize the various components of an embedded
   system and their interrelationship.
2. Modular architectural representations are typically the structures leveraged to
   structure the entire embedded project. This is mainly because the various modules
   (elements) within this type of structure are usually functionally independent. These
   elements also have a higher degree of interaction, thus separating these types of elements
   into layers improves the structural organization of the system without the risk
   of oversimplifying complex interactions or overlooking required functionality.