6 Part 6: V-Modell Reference Activities

6.3 Activities

6.3.10 System Design

6.3.10.4 Preparing Hardware Architecture

Purpose

Within the framework of the preparation of the architecture a »Hardware Architecture of the hardware unit shall be derived from the requirements and defined.

The process of preparing the architecture (see Figure 23) will start with the identification of the architectural drivers and, parallel to that, the definition of the evaluation criteria. Subsequently the architectural views will be identified and worked out.

The latter activity corresponds to the actual design process. The architecture that will have been worked out will be finally evaluated on the basis of the evaluation criteria and selected. The process of preparing the architecture may be carried out in several cycles.

Activity Flow

Figure 23: Activity Diagram "Preparing the Hardware Architecture"

6.3.10.4.1 Identifying Architectural Drivers

When identifying architectural drivers, principles for the design of a »Hardware Architecture shall be defined. This may include the following requirements:

• Comparable complexity of the hardware elements
• Minimum number of physical or logic interfaces
• Decoupling of safety-critical and safety-uncritical hardware elements
• Use of bought-out components, such as COTS products (in the form of products of the type External Hardware Module)
• Modularity and reusability

6.3.10.4.2 Determining Evaluation Criteria

Within the scope of this subactivity, different perspectives (views) on the hardware shall be defined (for this see also the description regarding Identifying Architectural Views in the activity Preparing System Architecture).

In the simplest case »Hardware Architectures will be a hierarchical decomposition of the hardware with the associated physical hardware elements, including the interfaces (structural view) and the description of the communication and interaction between the hardware elements or the hardware elements and the environment (protocol view).

It will be possible to define arbitrary additional views on the hardware, which may relate for example to the power consumption, the distribution of masses or the reliability of the hardware.

Appropriately several different views should be prepared to permit easy access and to improve the understanding of the architecture.

6.3.10.4.3 Identifying Architectural Views

Within the scope of this subactivity various perspectives on the hardware shall be defined. This will include for example

• the hierarchical decomposition of the hardware with the associated physical hardware elements, including the interfaces (structural view);
• the description of the communication and interaction between the hardware elements or the hardware elements and the environment (protocol view).

It will be possible to develop arbitrary views on the hardware, which may relate for example to the power consumption, the distribution of masses or the reliability of the hardware.

Appropriately several different views should be prepared to permit easy access and to improve the understanding of the architecture.

6.3.10.4.4 Preparing Architectural Views

Each identified hardware architectural view will have to be prepared (for this see also the description regarding Preparing Architectural Views in the activity Preparing System Architecture). This will include the following steps:

• Identification of the elements and their dependencies within a view,
• Selection of a suitable notation (for example graphically or in text form) for the representation of the view,
• Selection of a suitable tool for the development, preparation and representation of the view,
• Preparation of the view with the selected tools and notations.

Within the scope of the structural view it would be for example possible to prepare a detailed description of the data and signals of a »Hardware Unit with programmable logic. This will include aspects of the representation, such as an identifier, a format description, the range of values, the resolution and an introductory description, as a minimum requirement.

6.3.10.4.5 Evaluating Architecture

Based on the defined evaluation criteria, the architecture shall be evaluated. For this purpose it may be for example necessary to make analyses, to conduct simulations, to develop prototypes (rapid prototyping) or to build demonstrators.

If an architecture fulfills the evaluation criteria completely, it may be used as a basis for the further development process.

6.3.10.4.6 Preparing Set of Drawings

After the selection of the final architecture, the set of drawings of the »Hardware Unit shall be prepared for manufacturing. For this purpose the following activities shall be carried out:

• Preparation of sketches, construction plans and interface drawings,
• Description of the construction process,
• Identification of the materials,
• Preparation of the wiring diagram,
• Preparation of parts lists,
• Preparation of the connector board layout based on the wiring diagram,
• Preparation of design drawings,
• Preparation of connection diagrams.

As a rule, large parts of the set of drawings can be automatically generated by the appropriate tools.