Hardware pt 2 Flashcards
What is the Central Processing Unit (CPU)
Has the responsibility for execution and processing of all instructions and data in a computer. It also contains the. System clock and primary memory
What does the CPU consist of
*Control Unit (CU)
*Arithmetic and Logic Unit (ALU)
*Registers and Buses
What is a microprocessor
An integrated circuit, it contains the ALU and control unit to enable it to interpret and execute all instructions and carry out arithmetic operations
What is Von Newman architecture
Introduces the idea of the stored program computer. It introduces:
*The concept of a CPU
*The processor was able to access the memory directly
*Computer memories could store programs as well as data
*Stored programs were made up of instructions which could be executed in sequential order
Summaries the components of a typical CPU
*ALU: allows all arithmetic and logic operations to be carried out. Computers can have more than one ALU.
*Control Unit:
Reads instructions from memory. Signals are generated during the Fetch-Decode-Execute cycle to control all components of the computer.
The CU synchronizes data flow and program instructions throughout the computer.
*Registers: Registers can be general purpose or special purpose.
High speed areas of memory within a microprocessor/CPU—used to store small amounts of data, addresses or next instruction to be executed or current instruction being decoded
*System Clock: Used to produce timing signals on the control bus to ensure all functions are synchronized.
Changing clock speed can improve performance but there is always the risk of overclocking.
*System Buses:
Address bus(unidirectional): carries addresses throughout the system
Data bus(bidirectional): allows data to be carried to/from CPU/memory and to/from input-output
Control bus(bidirectional):carries signals from the control unit to all the computer components
*Memory:
The Random access memory (RAM) holds data , programs and the part of the Operating system currently in use.
RAM is often known as the immediate access store (IAS).
All data being used in programs needs to be transferred to the RAM.
Memory is made up of an address and its contents; the address identifies the location of data and instructions.
All memory locations are unique.
Primary memory also includes read-only memory (ROM) which cannot be altered;ROM contains start-up routines for the computer.
What is an embedded system
A combination of hardware and software designed to carry out a specific task
Summarize the Fetch-Decode-Execute cycle
Fetch:
*The PC contains the address of the memory location of the next instruction to be fetched from the MAR
*The address is then copied from the PC to the MAR using the address bus
*The contents of the memory location contained in the MAR is then copied into the MDR
*The contents of the MDR are then copied to the CIR and the PC is incremented by one so the next instruction can be processed
Decode:
*The instruction is now decoded so that it can be interpreted in the next part of the cycle.
Execute:
*The CPU passes the decoded instructions as a set of control signals too appropriate computer components
*This allows each instruction to be carried out in a logical sequence
What is the system clock
*The system clock defines the clock cycle used to synchronize all computer operations.
*timing signals are transmitted via the control bus.
What is overclocking
*Overclocking is caused by changing the clock speed in the BIOS, it can lead to overheating and to non-synchronized instructions which can cause the computer to crash.
What are caches
They store frequently used instructions and data, can speed up CPU performance. The larger the cache memory size the better the CPU performance.
What is found in an embedded system
*Microcontroller: Made up of a CPU with RAM, ROM and peripherals all embedded on a single chip to carry out a specific task
*Microprocessor: Integrated circuit consisting of CPU only (no peripherals)
*System on a chip: May contain a microcontroller as one of its components; usually includes a CPU memory, input/output ports and secondary storage all on a single chip
Summarize the Fetch-Decode-Execute cycle
Fetch:
* The PC contains the address of the memory location of the next instruction to be fetched from memory (MAR)
* The address is copied from the PC to the MAR using the address bus
* The contents of the memory location in the MAR are then copied to the MDR
* The contents of the MDR are then copied to CIR and the PC is incremented by one
Decode:
* The instruction is now decoded so that it can be interpreted in the next part of the cycle
Execute:
* The CPU passes the decoded instructions as a set of control signals to appropriate computer components
* This allows each instruction to be carried out in a logical sequence
How do barcode readers work
- Barcodes are a series of dark and light parallel lines of varying thickness
- They are read using a scanner that uses a red laser or red light emitting diode light source
- Reflected red light is read by photoelectric cells that create a digital sequence of dark and light e.g: LDDDDLD (or 011101 in binary)
- They are usually used one goods in a supermarket, but they can be used anywhere where an item can be scanned to identify it
- Each barcode is used as a key field to uniquely identify the record which gives the data about the product
How do QR codes work
- QR codes are another type of barcode made up of a matrix of filled-in dark squares on a light background
- QR codes hold more information than barcodes
- They can be used to advertize products, give automatic access to websites, store boarding passes electronically at airports and so on
- The camera is pointed at the QR code
- A stored app processes the image taken by the camera
- The browser reads the data generated by the app and decodes any web addresses embedded in the QR code
- Any weblinks are then sent to the smartphone or tablet
Summarize digital cameras
- Images taken by cameras can easily be transferred to a computer via USB port, Bluetooth or memory card reader
- The image through the camera lens is captured on photodiodes and converted into pixels which form an electronic matrix of the image which can be stored in memory
Summarize keyboards
- Each character on a keyboard has an ASCII value
- The computer is able to detect which key is pressed, which allows it to determine the character that was selected
- Entry of data via a keyboard is a slow process which is also prone to error and can lead to injury such as repetitive strain injury
Summarize microphones
- Microphones have a number of applications e.g: a sensor to input text into a computer or doing voiceovers on presentations and so one
- Microphones convert sound into electric currents of varying amplitude
- A diaphragm in the microphone vibrates and a copper coil and cone attached to the diaphragm create an electric current as the coil vibrates back and forth
- The current can be converted into digital data and then stored in a computer memory
