8.6 System Specification

System Specification and Decision Making in System Design

• System Specification is the controlling document in a project that includes product function, performance requirements, system interface, error handling procedures, and design constraints.
• Microprocessor tasks and product interaction with the environment should be identified and described in the system specification.
• A user's manual can be a useful way of providing specifications on how the product will interact with its environment.
• Design engineers must make important decisions without outside help in the system design phase, including build or buy ready-made parts, choice of microprocessor, and hardware or software implementation.
• Using commercially available systems is good practice for beginners in early design because of known cost and performance.
• The choice of microprocessor is important and should consider software availability, quantity availability, and experience of others.
• Development tools, including data sheets, programmer's guides, and software development tools, should be adequate to reduce development time and make programming easier.
• The processor should be fast enough and have enough addressing space to support the application at hand.
• Processors can be programmed to perform a wide variety of tasks, but there is still a need for some electronic hardware design in the interface.
• There are software/hardware trade-offs in achieving tasks that interact with external environment and devices, with cost as the deciding factor.
• Hardware implementation has a component cost but requires less development effort and has higher processing speed.
• Software implementation has no component cost but may involve a large amount of development effort and is generally slower in operation.