Slide 1

Interfacing and I/O Peripherals Dr John Cowell phones off (please) 1CSCI1412-HW-5

Slide 2

Overview Interface mechanisms buses: ISA / PCI, PCI Express, USB, AGP interface cards, PCMCIA Input devices keyboards, mice, joysticks, light pens, bar codes, magnetic card reader, OCR, scanner, microphone Output devices VDU, printers, plotter speakers CSCI1412-HW-52

Slide 3

3

Slide 4

Buses What is a bus? an electronic traffic lane through which electrical signals are carried from one chip to another chip most often used in the context of communication between the processor and other system components there are many different kinds of bus including ISA, EISA, MCA,SCSI and the local bus standards PCI and VL-Bus quoted from www.pctechguide.com CSCI1412-HW-54

Slide 5

A Potential Birds Nest Imagine connecting four chips to each other CSCI1412-HW-55 Now try to imagine what would happen with twenty chips!

Slide 6

The Bus Solution A bus comprises the actual physical components (wires, connectors, chips) and a set of protocols defining how it is used (timing, access methods) CSCI1412-HW-56 the busslots for extra peripherals

Slide 7

The System Bus The connection between the microprocessor and RAM is the most important bus it is made up of three component buses which are collectively known as the system bus or Front Side Bus address bus (location of memory) data bus (values to / from memory) control bus the system bus is now 64 bits wide 64 wires in parallel runs at speeds up to 1600 MHz on an Intel i7 short, delicate, single purpose CSCI1412-HW-57

Slide 8

The ISA bus The ISA (Industry Standard Architecture) bus was incorporated in the first IBM PC standard used to attached to peripherals and the expansion slots originally 4.77 MHz, now 8 MHz now 16 bit it was the fact that it was published as an open standard and was flexible enough to connect a wide variety of expansion cards that was the main reason for the success of the IBM PC still used today, although Intel and Microsoft have decreed that it is to be abolished CSCI1412-HW-58

Slide 9

EISA / MCA As the ISA bus was so slow (and because it was a fixed standard), there were some attempts to improve or enhance it MCA (Micro Channel Architecture) from IBM 32 bit, 10 MHz incompatible with ISA and not supported by Intel/MS therefore died out! EISA (Extended ISA) 32 bit, 8 MHz extended (32 bits v. 16) but still compatible successful for a while, but now superceded CSCI1412-HW-59

Slide 10

PCI Intel created a new standard: PCI (Peripheral Component Interface) 32 bit or 64 bit, originally 33Mhz, now 66 MHz fixed, independent of processor speed robust, upgradeable, reliable, compatible plug and play Intel and MS defined a specification to allow peripherals to be automatically detected and configured by the PC, rather than by the user In Express format now the standard for high speed peripherals hard disk and graphics controllers CSCI1412-HW-510

Slide 11

SCSI / SCSI-2 The SCSI (Small Computer System Interface) bus was defined by ANSI in 1986 used widely in non IBM-PC (esp. UNIX, Macs) originally designed for hard disk drives, now extended to CD- ROMs, scanners, faxes, etc SCSI-1: 8 bit, SCSI-2: 16 bit can be incorporated into PCs using a SCSI card commands issued at a higher level e.g. use logical block address (not physical location) SCSI devices need termination with resistors jumper connections on SCSI device CSCI1412-HW-511

Slide 12

AGP and PCI Express AGP used on older PCs for graphics - AGP 8x 2,100 MB/s Peripheral Component Interconnect Express - PCI Express,a standard for graphics applications (replacing AGP) Sometimes called PCI-E or PCIe Developed by Intel in 2004 PCI Express is serial and can transmit data in two directions at the same time. PCI is parallel and can only transit in one direction. Communication via lanes, each lane is a unidirectional point to point serial link Physical PCIe slots may contain 1-32 lanes in powers of 2, e.g. 1,2,4,8,16,32. Data is interleaved - successive byte are sent down successive lanes. CSCI1412-HW-512

Slide 13

PCIe - 1 In PCIe 1.1 released in 2004 each lane carried 250 MB/s PCIe 2.0 released in late 2007 500MB/s PCIe 3.0 due for release in 2010 1 GB/s As the number of lanes increase the transfer rate increases PCI Express 1x 250 [500] MB/s PCI Express 2x 500 [1000]MB/s PCI Express 4x 1000 [2000] MB/s PCI Express 8x 2000 [4000] MB/s PCI Express 16x 4000 [8000] MB/s PCI Express 32x 8000 [16000] MB An 8-lane PCIe 2.o carries as much as the fastest AGP CSCI1412-HW-513

Slide 14

PCIe - 2 All new graphics cards are now PCIe NVIDIA uses PCIe in its Scalable Link Interface (SLI) technology, to allow multiple graphics cards of the same chipset and model number to be run in tandem. ATI also has developed a multi-GPU (Graphics Processing Units) system based on PCIe called CrossFire. AMD and NVIDIA released motherboard chipsets which support up to four PCIe x16 slots, allowing tri-GPU and quad-GPU card configurations. CSCI1412-HW-514

Slide 15

PCMCIA The PCMCIA (Personal Computer Memory Card International Association) is both an organisation and a standard for the expansion of portables (laptops, handhelds, etc) loose collaboration of hardware and software industries rather than a single organisation originally a 16 bit standard, now 32 bit not really a true bus, more of a total interface specification including hardware design and software services can handle RAM, disks, graphics very flexible, generic, handles hot-swapping CSCI1412-HW-515

Slide 16

USB - 1 The problem Many different types of ports: serial ports, parallel ports, keyboard and mouse connections, joystick ports, midi ports etc. Requirements A way of connecting large numbers of devices. To replace legacy ports. Does not require specific interrupt resources Hot-pluggable. Plug and Play. The Universal Serial Bus (USB) developed as a solution Specification developed by Compaq, Intel, Microsoft and NEC, joined later by Hewlett- Packard, Lucent and Philip. The USB Implementers Forum, Inc as a non-profit corporation to publish the specifications and organise further development in USB. CSCI1412-HW-516

Slide 17

USB-2 Universal Serial Bus (USB) is replacing serial ports Three data speeds, Low Speed 1.5Mbits/s This was intended for cheap, low data rate devices like mice. The low speed captive cable is thinner and more flexible than that required for full and high speed. Full Speed - 12MBit/s This was originally specified for all other devices. High Speed 480Mbits/s The high speed additions to the specification were introduced in USB 2.0 as a response to the higher speed of Firewire. These speeds are the fundamental clocking rates of the system, and as such do not represent possible throughput, which will always be lower as the result of the protocol overheads. CSCI1412-HW-517

Slide 18

USB - 3 USB has a 'tiered star topology' in which there is a single host controller and up to 127 'slave' devices. Because the address field in a packet is 7 bits long, and the address 0 cannot be used as it has special significance. The host controller is connected to a hub, integrated within the PC, which allows a number of attachment points (often loosely referred to as ports). CSCI1412-HW-518

Slide 19

USB - 4 If 127 devices is not enough ! A further hub may be plugged into each of these attachment points. A device can be plugged into a hub, and that hub can be plugged into another hub and so on. M Maximum number of tiers is six. The length of any cable from hub to device is 5 metres. Could extend up to 30m with 6 tiers. For greater distances use another form of connection such as Ethernet. CSCI1412-HW-519

Slide 20

USB - 4 At any point in time, only the host OR one device can be transmitting at a time. When the host is transmitting a packet of data, it is sent to every connected device. Only one device, the addressed one, actually accepts the data. (The others all receive it but the address is wrong for them). One device at a time is able to transmit to the host, in response to a direct request from the host. CSCI1412-HW-520

Slide 21

21CSCI1412-HW-5

Slide 22

Input/Output Devices In essence input and output devices allow us (the users) access to the bits in the computer input devices convert information from human / analogue form into digital takes control information from the user output devices convert information from computer to human usable form provides control information to the user Human computer interaction (HCI) is the study of how we interact with computers e.g. the mouse: developed in mid 70s by Xerox ergonomic design tries to improve our HCI CSCI1412-HW-522

Slide 23

Keyboards The original qwerty keyboard was designed to deliberately slow typists down mechanical typewriters couldnt keep up! common letters put close together so that the same finger must be used (which is slow) common letters away from home positions (F/J) There are other arrangements of letters dvorak arranged to enhance speed Many variations on the basic theme ergonomic styles, such as MS natural numeric keypads, function and control keys foreign keyboards with special keys (accents, etc) CSCI1412-HW-523

Slide 24

How Keyboards Work The keys are arranged in a grid of wires a key press connects vertical to horizontal this is translated into a key number later translated by the OS into the character value CSCI1412-HW-524 often the switches are mechanical sometimes more basic conductive membrane different weights how hard to press clicks v. soft feel

Slide 25

Mouse There are a wide variety of types of mouse Right and left handed Foot operated. Virtually all have USB interface Wide configuration of buttons (e.g. For web navigation, giving presentations) Pseudo mice type devices e.g. Tracker balls, tracker pens Increasingly cordless with Bluetooth interface. Virtually all mice are optical An LED produces red light which hits a surface and is reflected back onto a sensor. The sensor sends the image to a Digital Signal Processor DSP for analysis. The DSP determines the speed and degree of movement. Latest versions use a laser for better tracking and less sensitivity to surfaces. CSCI1412-HW-525

Slide 26

Scanners A scanner takes an image and makes a digital representation of that image there are two main types of scanner hand held: the user moves the scanner over the image flat bed: image is placed on scanner: lens moves either of which can scan the image in colour or black & white different resolutions (dots per inch: dpi) there is a wide variety of software formats for storing the final image JPEG, TIFF, BMP, GIF, PNG, PCX, FAX (+more!) image processing software can manipulate & convert CSCI1412-HW-526

Slide 27

How a Scanner Works Light is shone onto paper, and reflections are received by light sensitive diodes CSCI1412-HW-527 pctechguide A light source illuminates the paper placed on the scanners glass plate: blank or white areas reflect more light The scan head moves below the paper and receives the light reflected from the paper The light is reflected by a series of mirrors The scanners lens passes light onto light-sensitive diodes which translate it into electrical current

Slide 28

Other Optical Devices Optical character recognition (OCR) is now usually software (often bundled with scanner) coverts the bits representing the image into a sequence of letters e.g. for a word processor now very accurate for good quality typed characters still quite poor at handwriting (needs training) Optical mark readers (OMR) are often dedicated hardware scanner & software rather than scanning the whole image, the OMR simply looks for marks in preset positions e.g. multiple choice exams, national lottery CSCI1412-HW-528

Slide 29

Bar Codes There are many different encoding schemes UPC (groceries), ISBN (books), Code 39 (parcels) Readers shine a laser at the bar code and detect the reflections received there are many physical forms of readers wands, guns, cards, prismatic (supermarket checkouts) CSCI1412-HW-529 Groceries (UPC) - A goods category manufacturer code centre bar guards product code check digit

Slide 30

Sound & Voice Recognition Many people have recognised the fact that typing is slow and laborious. Recent developments have made speech to text and text to speech applications more common. Text to Speech is more easy to achieve, but voices sound monotonous. This has been a part of MS development environments since 2005. Speech to text is more complex. A speech to text engine is included part of MS Visual Studio 2008 Success rate on untrained users is about 70% Great improvements after training. Not suitable for critical applications. CSCI1412-HW-530

Slide 31

Magnetic Devices Magnetic ink character recognition (MICR) specially shaped letters in magnetic ink the funny looking numbers on the bottom of cheques read directly by a special purpose scanner Magnetic strip readers these are pervading all aspects of everyday life credit / bank / store cards, ID cards bits are encoded as polarities on the magnetic strip on the back of the card CSCI1412-HW-531

Slide 32

32CSCI1412-HW-5

Slide 33

Output Devices In general output devices are conveying information (in usable form) to the user Monitor : the screen our main view of the computer: moving images printer Laser or ink-jet are the dominant technologies plotter specialised type of printer, usually for large size printing e.g. Architectural drawings loudspeakers providing sound, e.g. speech, games CSCI1412-HW-533

Slide 34

Sound There are two main components concerned with producing sound from a computer sound card the sound card is the device which turns bits of information into electrical signals to drive speakers speakers convert electrical signals into sound (vibrations of air) stereo: different sound out of each speaker tweeters: high-frequency, woofers: low-frequency Unlike audio CDs there are many different standards used for encoding sound in bits wav, midi, mpeg, mp3 CSCI1412-HW-534

Slide 35

Summary Interface mechanisms buses: ISA / PCI, PCI Express, USB interface cards, PCMCIA Input devices keyboards, mice, joysticks, light pens, bar codes, magnetic card reader, OCR, scanner, microphone Output devices VDU, printers, plotter speakers CSCI1412-HW-535