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Understanding Functional Requirements
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Let's start with functional requirements. These are essential since they dictate what the system must do. Can anyone give me examples of functional requirements in embedded systems?
How about turning on a motor based on a specific temperature?
Exactly! That's a great example. Functional requirements often start with 'The system shall...' Can anyone think of another example?
The system shall transmit sensor data every 100 milliseconds.
Right. 'Shall' indicates a mandatory action. Remember, functional requirements specify actions or behaviors. Let's also think of a hint: **P.A.S.S.** for Performance, Action, System, Services, which can help you remember these aspects.
Would storing configuration settings qualify?
Yes! You're catching on! Let’s summarize: functional requirements must outline the specific tasks the system must fulfill.
Delving into Non-Functional Requirements
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Now let's move on to non-functional requirements. These often determine how well the system functions. What kind of characteristics might these include?
Performance metrics, like how fast a system responds.
Correct! Non-functional requirements cover areas like performance, safety, reliability, and security. An acronym to remember these is **Q.R.S.C.P.U.**: Quality, Reliability, Safety, Cost, Performance, Usability.
Can you give an example for safety?
Certainly! A non-functional requirement example could be: 'The motor must stop immediately if an overcurrent condition is detected.'
So, non-functional requirements are not about what the system does, but how it does what it does?
Exactly! They impose constraints or conditions on the behavior. In summary, functional requirements explain what a system does, while non-functional requirements cover how effectively it performs those functions.
The Importance of Both Requirements
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Let’s talk about the importance of both functional and non-functional requirements. Why do you think they are both essential in embedded systems?
Because if the requirements are not clear, the system might not meet user needs.
Absolutely right! Clarity in requirements is critical. Can anyone think of the consequences of overlooking either type?
If we miss functional requirements, users might not get the expected services. But missing non-functional could lead to failures during operation.
Good observation! A failure in either could lead to catastrophic results, especially in safety-critical applications. So, in summary, always ensure that both types are well defined to achieve a robust system.
Introduction & Overview
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Quick Overview
Standard
Functional requirements specify what the system must perform, detailing services and functionalities, whereas non-functional requirements impose quality attributes such as performance and security. Both types are essential for successful embedded system development.
Detailed
Types of Requirements: Functional vs. Non-Functional
In embedded systems design, requirements are crucially categorized into functional and non-functional types. Functional requirements define what the system must achieve or what functions must be performed, focusing on the specific behaviors and outputs expected from the system. Examples can include actions like activating a motor or transmitting sensor data. On the other hand, non-functional requirements outline how well those functions should be performed, encompassing quality attributes like performance, reliability, safety, usability, and security. These requirements pose constraints and specify conditions the system must comply with during operation and development. The distinction between these two types of requirements is vital: while functional requirements clarify user needs and system functionalities, non-functional requirements ensure that the system is effective, reliable, and user-friendly. Therefore, both categories of requirements must be meticulously defined to achieve a robust design that meets user expectations and regulatory standards.
Audio Book
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Functional Requirements Overview
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A. Functional Requirements:
Definition: These define what the system must do or what functions it must perform. They describe the services the system should provide to its users or to other systems.
Characteristics: Typically expressed as actions, behaviors, or data transformations.
Examples in Embedded Systems:
- "The system shall activate the motor when the temperature exceeds 80 degrees Celsius."
- "The system shall transmit sensor data via SPI every 100 milliseconds."
- "The system shall display the battery level on the LCD screen."
- "The system shall store configuration settings in non-volatile memory."
Detailed Explanation
Functional requirements specify the exact functions or behaviors that a system should exhibit. They are crucial because they tell developers exactly what to build. Each functional requirement is framed around a specific action that the system must carry out. For instance, if a requirement states that the system should 'activate the motor when the temperature exceeds 80 degrees Celsius', it clearly communicates an action that must occur under specific conditions. Functional requirements are often specified in a straightforward language that can be easily understood by all stakeholders, including users and non-technical team members.
Examples & Analogies
Think of functional requirements like the rules in a game. For example, in soccer, a rule could be 'A goal is scored when the ball crosses the goal line between the goalposts.' Just like this rule defines what action leads to scoring, functional requirements define actions that the system must execute.
Non-Functional Requirements Overview
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B. Non-Functional Requirements (Quality Attributes):
Definition: These define how well the system performs its functions or what qualities it must possess. They specify constraints on the system's operation, development, or environment. They are often more challenging to quantify and verify than functional requirements.
Categories and Examples in Embedded Systems:
- Performance: Response time, throughput, execution speed.
- "The system shall respond to a critical alarm within 50 microseconds."
- "The control loop shall execute with a period of 1 millisecond ± 10 microseconds."
- Reliability: Likelihood of failure, fault tolerance, availability, mean time between failures (MTBF).
- "The system shall operate continuously for 5 years without failure."
- "The system shall recover from a transient power loss within 1 second."
- Safety: Prevention of harm to users or environment.
- "The motor shall immediately shut down if an overcurrent condition is detected."
- "The system shall ensure that two mutually exclusive actuators are never active simultaneously."
- Security: Protection against unauthorized access or attacks.
- "The firmware update process shall be cryptographically authenticated."
- "All sensitive data stored on the device shall be encrypted."
- Usability: Ease of use, learning, and user interface design.
- "The user interface shall be intuitive for operators with minimal training."
- Maintainability: Ease of modification, repair, and evolution.
- "The software shall be modular, allowing independent updates of driver components."
- Portability: Ease of adapting to different hardware or software environments.
- "The application layer shall be hardware-agnostic, using a well-defined HAL."
- Cost and Resource Constraints: Limits on budget, memory, CPU, power consumption.
- "The system shall operate on a single 3.3V power supply."
- "The maximum Flash memory usage shall not exceed 128 KB."
- "The average power consumption in sleep mode shall be less than 50 microamperes."
- Environmental Constraints: Operating temperature, humidity, vibration, EMC compatibility.
- "The device shall operate reliably in temperatures ranging from -40°C to +85°C."
Detailed Explanation
Non-functional requirements outline the quality attributes and constraints that the system must fulfill, going beyond what the system does to how well it does it. For example, performance requirements dictate how fast the system should respond to requests or how much data it should process, while reliability requirements ensure that the system functions consistently over time. Non-functional requirements often require careful measurement and testing to confirm that the system meets these standards, as they may not be as straightforward or clear-cut as functional requirements.
Examples & Analogies
Consider a car. While functional requirements specify that it must drive, stop, and accelerate, non-functional requirements would focus on how fast it accelerates, how much gas it consumes, and how safe it is during a crash. Both aspects are necessary for a complete understanding of a vehicle, just like functional and non-functional requirements together ensure a comprehensive specification of system expectations.
Definitions & Key Concepts
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Key Concepts
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Functional Requirements: Outline what the system must achieve.
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Non-Functional Requirements: Define quality attributes of the system.
Examples & Real-Life Applications
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Examples
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An example of a functional requirement: 'The system shall activate the motor when the temperature exceeds 80 degrees Celsius.'
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An example of a non-functional requirement: 'The system shall operate continuously for 5 years without failure.'
Memory Aids
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🎵 Rhymes Time
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Functional's the action, what the system provides, Non-functional's the quality, where performance resides.
📖 Fascinating Stories
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Imagine building a robot: it must know to move (functional), but it should also be fast and safe (non-functional) to be effective.
🧠 Other Memory Gems
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Remember: F.U.N. for Functional as 'What it does' and Q.S.R.C. for Non-Functional as 'Quality, Safety, Reliability, Cost.'
🎯 Super Acronyms
F.R.N.F. stands for **F**unctional **R**equirements, **N**on-functional **F**eatures.
Flash Cards
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Glossary of Terms
Review the Definitions for terms.
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Term: Functional Requirements
Definition:
Specifications that outline what a system must do or the specific functions it must perform.
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Term: NonFunctional Requirements
Definition:
Requirements that define how well a system performs its functions, specifying quality attributes like performance, safety, and usability.