4.7: section 5: computer organisation and architecture

• processor: Responds to and processes the instructions that drive the computer. • main memory: stores data and instructions that are to be processed • address bus: -sends the memory address of a word from the processor to CPU components • control bus: Sends control signals/lines between the I/O controllers and the processor • data bus: -sends data and instructions between CPU components • I/O controller: receive input and output requests from the processor and send device specific controls signal to the device

• instructions and data must be stored in the main memory to be executed • the machine code instructions are fetched from the memory one at a time using the same bus and decoded and executed by the processor used extensively in general purpose computing systems

• has separate memories for data and instructions • has separate buses for data instructions • used embedded Digital Signal Processing (DSP) • faster than Von Neumann as the instruction and data can be fetched at the same time

• used with embedded digital signal processing • embedded systems include special purpose built in computers which operate in real time • e.g. traffic lights, navigation systems, aircraft flight control systems

machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations.

Memory is divided into units called words. Word: a fixed size group of digits, typically 8, 16, 32 or 64 bits • Each word has its own specific memory address • when a processor wants to read a word of data from the memory it puts the address of the word onto the address bus

-the group of instructions that a processor can carry out. -Each type of processor has its own instruction set, so instructions for one processor may not be compatible with other processors. -usually stored in machine code

• data transfer • arithmetic operations • comparison operators • logical operators • branching • halt

• the operation code which corresponds to an instruction - this will include the addressing mode

-the data value the operation is acting on

-where the value represented in the operand is the actual data value

-where the value represented by the operand is the memory address holding the data

printed diagrams made of light and dark portions which contain information computers can read with a barcode reader. there are 1d and 2d barcodes

contain more information in the same amount of space but require more processessing to extract content

laser light source lens photodiodes mirror

• mirror directs light from the laser onto the barcode • light reflected by barcode passes through lens and is incident on the photodiode • photodiode turns light into electrical charge which can be measured and processed to form a digital signal • light portions of diode reflect most light wile dark portions absorb • pattern of light and dark stripes in barcode correpsponds to inary 1s and 0s

lens sensors: CMOS, CCD cells shutter filter-coloured cameras

• lens focuses light onto sensor • sensors convert light into electrical charge • sensors are made up of cells which represent pixles in the final image • shutter regulats the path of light between the light and sensor • in colour cameras there are multiple cells per pixel • each cell has a filter that only allows a certain wavelengt of light. • bayer filters have the same number of green, blue and red filters that let cameras produce images close to what the human eye sees

laser light source mirror drum toner roller fusers

• drum is positively charges • e laser is directed at its surface by the mirror. Areas on which the laser is incident are discharged, • this leaves an impressions of the page in electrical charge • toner roller dispenses negatively charged toner onto the drum • toner is attracted to positively charged portions of the drum and is applied to paper • paper is heated by fusers which fixes toner to paper • colour printers use the same process but have 4 colours of toner CYMK

chip with a small amount of memory coil of wire attachted to chip/antenna

radio frequency tags are a method of tranferring information wirelessly between a taga and a reader

passive: inducing enough power form reader to operate chip active: contain a small ower supply like a battery they can be read from much further away than passive tags

• reader emits radio waves which are picked up by tags antenna • power induced from these waves is enough to power a passive tag’s chip • the chip uses its antenna to emit a radio wave containING its information • the wave is picked up by the reader hich decodes the information