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Computer Science Revision Mindmap - Coggle Diagram
Computer Science Revision Mindmap
SLR1
Component Functions
Inside a CPU
CU
It issues control signals that contral components within the CPU
It fetches, decodes and executes instructions
ALU
Performs arithmetic and logical operations
Registers
Small amounts of high-speed memory contained within the CPU
They store small amounts of data that are needed for processing
Clock
Tiny quartz crystal that vibrates billions of times per second
Sends out a regular electrical pulse which synchronises all the components
Inside an Embedded System
Microcontroller
A self-contained compuiter on a single chip
Controls a specific function in a device
Sensor
Device thatr detects and responds to changes in the physical environment (light, heat, motion)
Changes are converted into a signal processed by a machine
Actuator
Coverts electrical signals into physical actions
They allow a sytem to control and manipulate various devices and mechanisms
Battery
Provides power for the embedded system to run
Buses
Address Bus
Carries address locations where data can be read from/written to
Unidirectional
Data Bus
Carries data to the CPU from the RAM
Carries Data from the CPU to the RAM
Bidirectional
Control Bus
Carries control signals to the CPU to other components
Sometimes carries signals back to the CPU
Unidirectional/Bidirectional
Storage
RAM
Random Access Memory
Volatile
Stores data that is being used by open applications
Gigabytes of data can be stored
ROM
Read Only Memory
Non-volatile
Stores start-up instructions for the computer
Megabytes of data can be stored
Secondary Storage
Why is it needed?
RAM is volatile (lost when device is switched off)
ROM is read only (you cannot make any changes to it)
Types
Optical
Works by shining a laser onto a disc
Pits and Lands are physically burned onto the disc
Lands are more reflective than pits so more light is reflected back to a sensor
A land is 1 and a pit is 0
Magnetic
Has a magnetisable surface
A typical magnet has a North and South polarity
These states store 1s and 0s
Solid State
Works by a flow of electricity forcing electrons into floating gates between two oxide layers
This changes the charge of the floating gate which is measured in 1s and 0s
What is an embedded system?
A small computer part of a larger device or machine
Controls the device and allows the user to interact with it
Fetch-Decode -Execute Cycle
Fetch
1) The CPU places the memory address of the next instruction on the address bus
2) The CU sends a read signal along the control bus tp the memory
3) The content of the specified memory location is transferred along the data bus to the CPU and stored in the registers
Decode
The CU looks up the instruction in the CPU's instruction set (a list of all the operations it can carry out)
Execute
1) The CU coordinates the other components of the CPU to carry out the operation
2) If an arithmetic or logic operation required, the CU signals that it is to carry it out
The Cycle Repeats
SLR2