CSE491_Computer_Interfacing_and_Peripherals_Lec1.pdf
- 1. CSE491 Computer Interfacing and Peripherals Instructor: Abdelhameed Sharaf Schedule: Every Saturday ( Lectures) from 11:00 AM to 01:00 PM @ SS 208 OR from 01:00 PM to 03:00 PM @ 315 PH ( Lab/Tut.) Saturday: Sec1: 03:00 PM to 06:00 PM Tuesday: Sec2: 11:00 AM to 02:00 PM Sec3: 02:00 PM to 05:00 PM Wednesday: Sec4: 11:00 AM to 02:00 PM Course Content Main Interfacing Units Direct Memory Access Synchronous and Asynchronous Computer Communications Parallel and Serial Communications Peripherals Types and Its Connections Channel Programming Synchronous and Operation Control Case Study: Using C-Language Grading System First Exam 20 Pts., Week 6 (first 4 Second Exam 20 Pts., Week 11(the Assignment/Absent 20 Pts. , Weeks 5 and 10 Final Exam 90 Pts.
- 2. Main Textbooks: • THE INTEL MICROPROCESSORS 8086/8088, 80186/80188, 80286, 80386, 80486, Pentium, Pentium Pro Processor, Pentium II, Pentium III, Pentium 4, and Core2 with 64-Bit Extensions Architecture, Programming, and Interfacing, BARRY B. BREY Other Textbooks: • Computer Peripherals for Micro Computers, Microprocessor and PC by Levis Hahensteu. • Computer Peripherals And Interfacing by Priti Srivastav- Ishan Publication. • Computer Peripheral & Interfacing by Gourav Gupta, Eagle Prakashan, Jalandhar. • Microprocessors and Interfacing by Hall, Douglas: McGraw Hill.
- 4. Peripherals are any device that can be attached to a CPU, e.g. hard disk, mouse, printer. Peripherals are slow. They hold up the CPU from carrying out its’ tasks. For Example - playing a game and it needs to load the next level. The level is being read from the CD and written to memory. What is an interface? The interface is the combination of hardware and software needed to link the CPU to the peripherals and to enable them to communicate with the CPU despite all their differing characteristics. The hardware is the bit you connect the cable into e.g. USB, parallel Firewire. The software is the driver disk that you usually need to install when you get the device, e.g. printer diriver.
- 5. Computer peripherals all have different characteristics. For example, they may: Have different data transfer rates; Use a wide variety of codes and control signals; Transmit data in serial or in parallel form; Even work at higher voltages than the CPU; & All operate at much slower speeds than the CPU. The main functions of an interface that you need to know about are: Buffering; Converting data to and from serial and parallel forms; Converting data to and from analogue and digital forms; Voltage conversion; Protocol conversion; & Handling of status signals. Buffering: This is an area of RAM within the interface which stores the data while in transmit between the processor and the peripheral. The interface uses the buffer to temporarily store the data it is working with. It also uses the buffer to compensate for the differences in speed between the peripherals and the CPU by temporarily storing incoming data so that the faster CPU can process it in manageable blocks rather than waiting for the slower peripheral. Converting data to and from serial and parallel forms: Data transmission is the passing of data from one device to another. A serial interface uses serial data transmission; A parallel interface uses parallel data transmission. Serial data transmission - is when data is transmitted along a communication channel one bit after another in sequence. Very slow but efficient over long distances.
- 6. Parallel data transmission - transmit several bits of data simultaneously across a series of parallel channels, often transmitting 16 or 32 bits at a time. Very fast but only suitable for short distances. The buses internal to the processor are parallel channels. Any data coming from a serial device has to be sent to an interface which buffers the data then converts it to parallel form before it is passed to the processor. 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 Serial data format Interface Parallel data format Converting data to and from analogue and digital forms: Analogue signals – many electrical signals are analogue signals. These signals vary between two limits. Analogue signals that are sent in from peripherals to the digital form that the CPU can handle. If you could see an analogue signal it would look roughly like this: Digital signals – computers can only work with digital signals, which have only two values – on or off. A digital signal therefore consists of a series of “on’s” and “off’s”. An on signal is represented by a 1 and an off by a 0 0 1 1 0 0 1 1
- 7. ADC and DAC A computer is connected to a peripheral by an interface. This interface has to be able to change the digital signals from the computer to an analogue signal that the other device can understand. This is done by a DAC – Digital to Analogue Converter. Signals can be changed in the other direction by an ADC – Analogue to Digital Converter. Voltage Conversion Peripherals send data using a different voltage from that used by the processor and its associated components on the motherboard of the computer. An interface is used to compensate for these differences. Protocol Conversion A protocol is a standard that enables the connection, communication and data transfer between computers or between a computer system and a peripheral. Protocol conversion means ensuring that the protocols used by the peripheral can be understood by the computer it is attached to and vice versa. Handling of Status Signal The purpose of the status information is to show whether or not a peripheral device is ready to communicate. This information is used to inform the user of a problem requiring attention. Some printers Buffers and spoolers are terms generally associated with printers. The terms are not dedicated to printers but that is the context that will be described.
- 8. What is a Buffer? A buffer is an area of memory used for the transfer of data between a computer and a peripheral. A buffer provides temporary storage of data. Using a buffer provides a link between a device and the processor and helps compensate for any differences in their working speeds. Why use buffers? Peripherals operate at much slower speeds than the CPU. Using buffers helps the computer system compensate for the differences in operating speeds between CPU and its peripherals. When transferring data out to a peripheral such as a printer, the processor can transfer it faster into the buffer and the buffer will send it to the printer at a speed that the printer can cope with. Why use buffers? The use of buffers reduces the frequency with which the CPU is interrupted to deal with input. Data from a keyboard is stored in a buffer until there is a larger amount of data for the CPU to process. Spoolers Spooling is another technique used in the transfer of data to a slow peripherals. In this case the data intended for the peripheral, the best example is a printer, is transferred to storage, often a hard disk. Then when the processor is idle it will transfer the data to the printer at an acceptable speed. This is also called background printing. This frees up the much faster CPU to process other tasks. Spooling is another possible method of improving system performance.
- 9. Buffer v’s Spooler If the CPU is very busy and doesn’t get much idle time then spooling can be a very slow process. Spooler v’s Buffer A buffer is limited by the amount of RAM whereas a spooler uses backing storage which has a very large capacity. Use BOTH for optimum efficiency. New interfaces are continually being developed. One focus of development is to increase the speed at which interfaces allows the peripheral and computer to communicate. Another aim is to allow wireless communication between peripheral devices and the CPU. Interface speeds are measured in Megabits per second (Mbps). N.B. do not confuse Megabits and Megabytes Manufacturers normally use Megabits per second in their advertising as this allows them to print larger numbers on their advertisements.
- 10. One example of increasing interface speeds is the development of the USB 2 and the Firewire 800 interfaces. The USB 2 improves upon the maximum 12 Mbps speed of the USB 1 interface by 40 times to 480 Mbps. The Firewire 800 interface provides 800 Mbps, double the speed of the Firewire 400 interface. Interface Description RS232 Recommended Standard (Serial) SCSI Small computer Systems Interface ( Parallel) IDE Integrated Drive Electronics SATA Serial Advanced Technology Attachment – up to 1.5Gbps IEEE Institute of Electrical and Electronic Engineers e.g. firewire MIDI Musical Instrument Digital Interface PCI Peripheral Component Interconnect PCMCIA Personal Computer Memory Card International Association USB1 & 2 Universal Serial Bus The use of interface standards by a computer manufacturer means that their computers will be able to connect to peripherals using the same standards. The use of interface standards by peripheral manufacturers means that their peripherals will connect to a computer which uses the same standards. Makes them COMPATABLE!!! Interface Description Transfer Speeds USB1 Universal Serial Bus Fast transfer rate: A means of connecting 12 MBPS for fast external devices devices USB2 An improvement of the Up to 480 Mbps USB. Firewire A high speed serial interface In its latest version, used for connecting audio/ IEEE 1394b, up to a visual and multimedia max of 800Mbps. applications like digital 3.2Gbps are under camcorders. Development. Current trends in wireless communication include the standards WiFi and Bluetooth. Bluetooth and WiFi both use radio waves at the same frequency. Radio waves can pass through most materials and walls, and devices do not need to be pointing at one another, unlike, infrared data transmission (TV remote control).
- 11. Bluetooth Bluetooth can make short-range links between personal devices, such as mobile phones and headsets, palmtops (PDA) and laptop (notebook) computers. Bluetooth is also used for wireless keyboards and mice. It is expected that later versions of Bluetooth will be able to transmit data at a speed of 2 Mbps and for longer distances WiFi WiFi stands for the Wireless Fidelity Alliance. The main use for WiFi is in wireless local area networking (WLAN). WiFi devices have typical ranges from 15 to 50 meters and typical data transfer rates from 5 to 20 Mbps. A solid-state storage device contains no moving parts. Examples include flash cards and USB flash memory Both of these types of device contain the same type of backing storage medium, namely flash ROM. The effective difference between them is that they use different interfaces to connect to a computer system or another peripheral. Flash cards are used mainly for data storage in cameras, although they can hold any type of program or data file. There a number of different standards of flash cards. Each digital camera normally uses only one type of flash card Specialised card readers have been developed which have ‘slots’ to fit all the different varieties of flash cards. So called ‘all-in-one’ devices (printer, scanner, photocopies) have slots into which flash cards may be placed. This allows documents to be printed directly from the card, without a computer system having to be connected.
- 12. There are two types of USB Flash Memory, according to the type of interface being used. The are USB 1 and USB 2. Most of these devices are now compatible with USB 2. USB2 devices are always backwards compatible. In this case the speed of access will be USB 1 Solid-state storage devices are small. Flash cards can fit inside the camera. USB flash memory can fit on key rings and in watches. Solid-state storage devices are robust because they have no moving parts. This means that they are ideal for wearing because they are unaffected by vigorous movement. iPods take advantage of this feature of Solid-state storage devices. Solid-State storage devices use less power than hard disk drives. This lower power requirement means that a music player which uses solid-state storage will play music for a longer time relative to a hard disk-based music player with the same battery capacity. Solid-state storage devices are available in a range of capacities, from 256 Mb to 8 Gb (at the time of writing). USB flash memory has now replace floppy disk as a convenient, portable storage medium, which can fit into almost any modern computer system. USB flash memory is used for security applications. One type has fingerprint recognition and another type works with security software to prevent a computer system from starting up unless the USB flash memory is plugged in.
- 13. Increased capacity DVD The DVD-Recordable format capacity was increased with the introduction of the dual layer DVD-R disk with a capacity of 8.4 Gb (Single –layer DVD-R capacity is 4.7 Gb) Most computers now incorporate this dual layer drive. Blu-ray Blu-ray disc (BD) is the name of the next generation optical disc format. The format was developed to enable recording, rewriting and playback of high- definition video (HD). The format may become a standard for PC data storage and high-definition movies. Increased read and write speeds Faster interfaces are constantly being developed, e.g. USB 2, Firewire 800, with speeds of 480 Mbps and 800 Mbps, respectively Reduced Physical Size In 2004, Guinness World Records certified that Toshiba’s 0.85 inch diameter hard disk drive as the smallest hard disk drive in the world. Lower Cost Per Unit of Storage In 1995, a 100 Mb capacity hard disk drive cost £300. In 2005, a 100 Mb capacity ZIP drive cost £5, and a 512 Mb USB flash memory cost £25. Implications of Development Trends One implication may be that new peripherals and media may not work with old ‘legacy’ hardware. An older computer may not have a USB port, or if it does, it may not be USB 2, only USB 1. A DVD re-writer may not be able to read or write to new disk formats. Care must also be taken with archived data, to make sure that it is regularly copied to a current storage format so that it can always be accessed. In 2004 we say some electrical stores discontinue the sales of VHS video recorders in favour of DVD. Digital video cameras, which record directly to DVD instead of tape are now common.
- 14. 54 For the Higher course you need to be aware of how peripherals work and of the current specifications and trends. You should be aware of the following characteristics for each type of device: • capacity • speed • cost • type of interface • resolution pctechguide.com howstuffworks.com 55 • speed • resolution Keyboards generally follow the standard Qwerty layout although new innovative designs are available which attempt to improve user comfort and ease of use. n/a(not applicable) Speed of input is determined by the user’s typing ability. This is always very slow in computer terms and so speed is not a performance issue. 56 • capacity • cost • type of interface A keyboard has a very small buffer to store several keypresses but again capacity is not particularly relevant for keyboards. Keyboards are inexpensive items with prices ranging from £8 up to £50 and more for more stylish models. Manufacturers include Microsoft, Logitech and Benq. The PS2 (Personal System 2) interface was the standard but USB, Bluetooth and infra red are becoming more common.
- 15. 57 Scanners are used to convert graphic images into a digital format suitable for processing in a computer. Text can also be input when the scanner is used with Optical character recognition (OCR) software. • resolution The resolution of a scanner is measured in dots per inch (dpi). Note that 600 dpi means that every square inch has 600 x 600 dots = 360000 dots. The bit depth also affects quality with modern scanners offering 48 bit depth. 58 • speed The speed of a scanner is measured by how long it takes to scan a page at a particular resolution and bit depth. • capacity • cost • type of interface n/a Scanners cost from £50 to £300 depending on features. Manufacturers include Canon and Epson. The USB 2 interface is the standard with SCSI and Firewire also available. 59 A sound card takes an analogue sound and converts into a digital one.The sound is sampled by listening and measuring the sound every nth fraction of a second and storing the sample as a digital number. The sampling rate determines how often per second a sample is taken. CD quality samples at 44.1 kHz = 44,100 times per second. The sample size/bit depth determines the range of sounds which can be recorded each time. CD quality works at 16 bit depth which gives a range of 65,536 different sounds. 60 • speed n/a • capacity • cost • type of interface n/a Sound cards cost from £10 to £200 depending on features. Manufacturers include Creative Labs and Terratec. The PCI (Peripheral Component Interconnect ) interface is the standard with USB and Firewire also available.
- 16. 61 A digital camcorder takes moving images and converts them into a series of individual digital images. A CCD (Charge coupled device) detects light intensity and converts it into an electrical signal. • resolution The number of pixels in the CCD can affect quality. More expensive models have 3 CCDs, one for each primary colour, which also improves quality. A high optical zoom also allows good quality. 62 • speed Digital camcorders allow video display at 25 frames per second following the PAL standard which is used in most of Europe. • capacity • cost • type of interface The capacity of a camcorder depends on the type of backing storage used. These include MiniDV, Digital8, Hi8 tapes and optical DVD. Costs range from £200 to £3000 depending on features. Manufacturers include Sony, Canon and JVC Firewire is the standard interface for digital camcorders. 63 A digital camera takes a still image and converts it into a digital image. A CCD(Charge coupled device) detects light intensity and converts it into an electrical signal. • resolution The number of pixels in the CCD affects quality. CCDs of 4 megapixels and upwards are now common. Cameras typically use 24 bit depth for colour. A high optical zoom also allows good quality. 64 • speed Shutter speeds are relevant for taking photographs in different situations, e.g. sports shots, night scenes. • capacity • cost • type of interface The capacity of a camera depends on the type of backing storage used. These include SD, XD, Compact flash which are all solid state memory cards, and a microdrive which is a miniature Hard drive. Costs range from £40 to £5000 depending on features. Manufacturers include Fuji, Olympus, Canon and Nikon USB 2 is the standard interface for digital cameras.
- 17. 65 Tiny droplets of ink are heated and explode onto the page. Printers can print text and graphics, colour and a range of greyscales. • resolution Resolution is measured in dpi and 4800 x 1200 is typical. 24 bit depth is commonly used for colour. • speed Printer speed is measured in pages per minute (ppm). The speed depends on the size of the page and the complexity of the image being printed. 66 • capacity • cost • type of interface Printers store data about to be printed in a buffer. A large buffer will allow the user to begin other work on the computer while the printer is still processing the page. Costs range from £40 to £300 depending on features. Manufacturers include Epson, Lexmark, Canon & Hewlett Packard (HP). USB is the standard interface for modern inkjet printers with older models using serial or parallel interfaces. Running costs for inkjet printers are very high as cartridges have a limited capacity and are very expensive 67 Lasers write a page image onto a special drum as an electrostatic charge. The charged drum attracts toner particles which are transferred to the page and heated to fuse the image onto the paper. • resolution Resolution is measured in dpi and 600 x 600 is typical. Monochrome models are very common in offices and colour models are coming down in price. • speed Printer speed is measured in pages per minute (ppm). The speed depends on the size of the page and the complexity of the image being printed. 68 • capacity • cost • type of interface Printers store data about to be printed in a buffer. A large buffer will allow the user to begin other work on the computer while the printer is still processing the page. Costs range from £70 to £13,000 depending on features. Manufacturers include Epson, Lexmark, Canon & Hewlett Packard (HP). USB, serial, parallel and ethernet interfaces are used for laser printers. Running costs for laser printers are low as laser toner cartridges have a larger capacity than inkjets. Laser toner for colour lasers however is still very expensive.
- 18. 69 Two techniques are used with printers to cope with the fact that they work slowly compared to the processor. These involve the use of buffers and spoolers. Buffer You have already met the concept of buffering, using RAM to store data until the printer is ready to process it. Look back at slide 3 for more details 70 Spooler Spooling is a similar technique but here the file to be printed is: On our school network every time you print, a spool file is created and sent to the server for printing. The server then takes over the job of sending it down to the printer when the printer is ready. • Sent to the computer’s hard disk for temporary storage. • Stored in a queue and sent to the printer in stages as a a background job during the processor’s idle moments. This can slow down printing but allows the user to carry on with other tasks while printing is taking place in the background 71 CRT Monitors are large and bulky and use a similar technology to traditional television sets. The Cathode Ray Tube is the bulky part which sticks out at the back. • resolution Resolution is measured in dpi and CRT monitors can display at different resolutions. The size of the display directly affects resolution. An image on a 21-inch monitor with an 800x600 resolution will not appear nearly as sharp as it would on a 15-inch display at 800x600. • speed n/a The refresh rate is the number of times that the image on the display is drawn each second. A CRT monitor with a refresh rate of 72 Hertz (Hz) cycles through all the pixels from top to bottom 72 times a second. A low refresh rate means that the screen flickers and this can cause headaches and eye strain. • capacity • cost • type of interface n/a Costs range from £50 to £600 depending on size and features. Manufacturers include Samsung, Phillips, Viewsonic. The VGA (Video Graphic Array) interface is common with the new DVI (Digital Visual Interface) digital interface becoming more popular.
- 19. 73 Thin Film Transistor(TFT) Monitors use Liquid Crystal Display(LCD) technology to create monitors which are very slim and light. These are used on laptops and are rapidly becoming the standard type of display on desktops. • resolution Resolution is measured in dpi and TFT monitors are built with a particular resolution for best quality. Lower resolutions can be set but quality is poor. 1024 x 768 is common for laptop displays. This requires 2,359,296 transistors etched onto the glass. 74 • speed n/a There is no need to worry about refresh rate or flickering on a TFT monitor as transistors are either on or off. Due to manufacturing limitations TFT panels virtually always have some dead pixels which do not display correctly. • capacity • cost • type of interface n/a Costs range from £100 to £1600 depending on size and features. Manufacturers include NEC, Sony, LG. The VGA interface is common with the new DVI digital interface becoming more popular. 75 Hard Disks and floppy disks are the main examples of magnetic disk with floppy disks rapidly becoming obsolete due to their limited capacity of 1.44 Mb. • resolution n/a The read/write head moves to the required track and waits until the requested block spins past the head. The following characteristics refer to hard disk. 76 • capacity • cost • type of interface The capacity of modern hard disks ranges from 500 GB to 2 TB. Costs range from £30 to £160 depending on capacity and type of interface. Manufacturers include Maxtor and Seagate. Interfaces include IDE, SCSI, ATA and SATA. • speed Speed of access is important. The main factor here is the rotational speed of the disk with typical figures being 5,400 or 7,200 rpm. (Revolutions per minute) The type of interface also affects the speed of access.
- 20. 77 These include CD-ROM, CD-R, CD-RW, and their DVD equivalents. • resolution n/a The disk surface is a mirror covered with billions of tiny lands and pits that are arranged in a long, tightly wound spiral. A laser reads and interprets the information as bits of data. ROMs are read only. R can be written to once but not erased. RW can be written to and erased using special software. 78 • speed CD Speed is measured as a multiple of single speed audio which runs at 150 Kbps. Speeds for reading and writing differ with reading speed normally being the fastest. Single speed DVD is 1,250 Kbps Typical speed is now x52. and x16 speed is common. • capacity CD – DVD – 650 MB Between 4.7 GB and 17 GB depending on single/double sided, single/double layered. 79 • cost • type of interface Costs range from £10 to £130 depending on type and whether the drive is internal or external. Manufacturers include Pioneer, Lite-On and NEC. Interfaces include IDE, USB2 and firewire. 80 Magnetic tape drives are still commonly used for backup purposes although removable magnetic disks and optical RW technology can now also be used for backups. • resolution n/a Tape drives are relatively expensive but tapes are cheap. The school network backs up all user data files every night at midnight and five generations are kept. Tapes have a higher capacity than any of the optical media is use today.
- 21. 81 • speed Tapes allow serial/ sequential access and so their use is generally restricted to making backups. Transfer rates range from 2 to 30 Mbps depending on model and price. • capacity Capacities vary widely depending on model and price. Data can be stored in a compressed format which increases capacity but reduces transfer rates. Figures up to 1.3 TB were found on current price lists. (June 2009) 82 • cost • type of interface Costs range from £80 to £6,000 depending on type, capacity and data transfer rate. Interfaces include IDE, USB and SCSI. Manufacturers include Seagate, Travan and Hewlett Packard. 83 Solid state storage devices have no mechanical or moving parts and use integrated circuits rather than magnetic or optical media. Current technology means that capacity is lower than magnetic or optical media but costs are falling and capacities are increasing. Data transfer takes place at very high speeds and the devices are very robust. Flash cards are a popular form of solid state storage and are commonly found in digital cameras and mobile phones. 84 • speed With no moving parts, data transfer speeds are high at up to 480 Mbps using a USB2 interface • resolution n/a Memory sticks have virtually replaced floppy disks as a portable storage medium being easy to carry around. Some even double up as key rings or mp3 players.
- 22. 85 • cost • type of interface Costs vary up to £45 depending on type and capacity. USB 2 Manufacturers include Crucial, Kingston and Sony. • capacity Capacities vary widely depending on type. Figures from up to 16 GB were found on current price lists. (June 2009) 86 Solid state storage is replacing floppy disks as the portable medium. DVD is replacing CD as the main optical drive in computer systems. Blu Ray is now the standard for High definition DVD technology. It won against its rival Capacities for all devices are increasing and cost per byte is falling. HD-DVD.