1. CHAPTER Serial and Parallel Communication © N. Ganesan

2. Chapter Objectives Explain serial communication –Standards, ports, resources etc. Show a few examples of serial communication connections used in practice Describe the features of parallel communication –Standards, use etc.

3. Chapter Modules Serial communication Newer serial communication technologies Serial communication connections Parallel communication

4. MODULE Serial Communication

5. Definition of Serial Communication Bit by bit transmission of information in series AB Travels in series

6. Serial Communication Implementation Popular implementation is known as the RS-232 serial connection found in microcomputers Newer type of serial connections –Universal Serial Bus (USB) –IEEE 1394 serial connection that is also dubbed as the Fire Wire connection

7. RS-232C Serial Standard The most popular standard Conforming serial ports –Micro –Minis and mainframes Sometimes these ports are also known as the asynchronous ports It is also possible to conduct synchronous transmission through these ports as well

8. Purpose of the Serial Ports Serial Interface Parallel Digital Data Serial Digital Data Out In Expansion Bus

9. Standard Serial Ports on a Computer

10. Serial Port Identification Source: Black Box

11. Male and Female Connectors Pins Holes Typical serial port Typical parallel port Source Black Box

12. Differentiating Between Serial and Parallel Ports Serial Male Port Parallel Female Port

13. Serial Cable DB25 Connector DB9 Connector Source Black Box

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15. Serial Communication Related Factors Comm ports –Comm1 to Comm4 for example ASCII terminal connection –DEC mini computers –UNIX based multi-user computers Other factors involved in serial communication –Interrupt –I/O address

16. MODULE Properties of Serial Ports

17. Support for Serial Ports Both hardware and software support are required for the functioning of serial ports A microcomputer is supplied with two standard ports –Additional ports can be installed

18. Operating System Support Earlier operating systems –Supported four serial ports Today’s operating systems –Support a larger number of serial ports For most practical purposes, four serial ports are considered sufficient in a microcomputer –Only two, namely com1 and com2, are in widespread use

19. Port Properties Com 1 Com2 Com3 Com4 IRQ I/O Address Direct Memory Address (DMA) Channel

20. Assignment of Values The assignment of the respective values for each port must be unique An IRQ, I/O address or DMA conflict can lead to a disruption in the execution of an application

21. IRQ and Address Assignment PORTIRQADDRESS ------------------------------------------------------------ 143F8-3FF 232F8-2FF 3 4 These values should not normally be changed.

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23. Demonstration of IRQ Assignment

24. MODULE Faster Serial Ports and Summary

25. Older and Newer Serial Ports Older serial ports operated at a slower speed The newer serial ports operate at a faster speed The newer serial ports are equipped with a new processor The hardware in question is known as the UART processor

26. Enhanced Serial Ports UART 16550/ 16650 Com. Port The newer processor is required for communication at speeds of 115,200 bps Universal Asynchronous Receiver Transmitter (UART)

27. ISDN Line Requirement In theory, the maximum speed over a single ISDN line is approximately 128K bps If necessary, enhanced serial ports can be installed by installing a board containing the enhanced ports

28. UART-based Ports

29. In Summary Two standard serial ports are present on a microcomputer Resources –IRQ, I/O Address and DMA Port settings –Communication speed, length of the data bits etc. Later versions of the UART chip are required to support high speed communication through the serial port

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31. MODULE Newer Serial Communication Technologies: Universal Serial Bus (USB) and FireWire (IEEE 1394)

32. Universal Serial Bus Being introduced as a high-speed “replacement” for the traditional RS-232 port USB has a bandwidth of 12M bps which is 1.5M Bps It is therefore considerably faster than the RS-232 port that operates in the region of 115+ K bps Devices, for instance, can be daisy- chained

33. Daisy Chaining of USB Devices Computer Device 1 Device 2 Device 3 USB Connection Out In USB Port

34. Sample USB Devices Keyboards Monitors Digital Cameras etc.

35. Support for the Deployment of USB in Microcomputers There are two requirements for USB implementation One is the presence of USB ports in the microcomputer The other is the support required from the operating system to operate the USB Most motherboards now have built-in support for USB Not all versions of the Windows OS support for USB

36. Operating System Support for USB The newer operating systems or the later versions of some of the older operating systems support USB –Windows 98 –Windows 95 OSR2 In accordance with USB standards, these operating systems support hot plug-and-play for USB devices

37. Hot Plug-and-Play The ability to connect a device to the computer while a computer is in operation As the device is connected, the OS would: –Recognize the device –Configure the device There is no manual intervention in the above process

38. Advantages of USB Over the RS- 232 Port Higher speed Ability to daisy chain different devices Support for hot plug-and-play

39. IEEE 1394 Standard (Fire Wire) Very new introduction Next level in serial communication after USB Bandwidth is 400M bps or 50M Bps In theory therefore, it can replace SCSI and IDE used for connecting hard disks Fire Wire’s impact is most likely to be felt in multimedia applications involving audio and video

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41. MODULE Serial Communication Connections

42. Modem Connection Modem Computer RS-232C Serial Digital Signals ITU Serial Analog Signals

43. Unix Computer Connection ASCII Terminal Micro- computer ASCII Terminal RS-232C Connection Multi-user Micro (Unix) Multiple serial ports

44. Multiple Port Support Interface Card Multiple Ports

45. Popular Unix Configuration Microcomputers as terminals TCP/IP Central Unix server

46. Remote Access Server Server with Multi-serial Ports Modem RS-232C Connection Modem Dial-in access LAN

47. LapLink Connection Desktop Computer Laptop/ Notebook/ Computer RS-232C Serial Lap-link Connection Note: Lap Link serial cable is specially wired

48. X.25 Standard Used in WAN connections X.25 is used in the U.S. Its equivalent X.21 is used in Europe Today, the above older technologies are being replaced with newer digital technologies –ATM –Frame Relay etc.

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50. An X.25 WAN Connection WAN LAN Terminal X.25 Gateway Enterprise Comp. Sys. X.25 The equivalent X.21 is used in European countries

51. X.21 Standard Used for WAN connection Used largely in Europe

52. MODULE Parallel Communication

53. Definition of Parallel Communication Transmission of information over multiple links between two points –Multiple electronic links

54. Parallel Transmission Multiple links

55. IEEE 488 Parallel Standard Established by IEEE Used extensively in parallel Communication Examples: –Computer to printer connection –Lap Link connection Does not play as important a role as the serial standard –Hardly any parallel long distance links in practice

56. New Uses for the Parallel Port Connecting devices such as an external mass storage device

57. Parallel Port and Serial Ports in a Microcomputer DB25F DB9M DB25M Serial Com1: Serial Com2: Parallel LPT1:

58. Parallel Port Resources Resources must also be assigned to the parallel port as well –IRQ and I/O address range Sample values assigned for LPT1 –IRQ 7 –I/O address range 378 - 37f –These values should not be changed in general

59. Summary A microcomputer is equipped with one standard parallel port Additional parallel ports can be installed Used extensively for connecting a printer –Used for connecting other devices as well Needs to be assigned resources Identified by the DB25 female connector

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61. Parallel Port Resource Assignment Demonstration

62. MODULE Newer and Faster Parallel Ports

63. Popular Introductions Enhance Parallel Port (EPP) Extended Capability Port (ECP)

64. EPP and ECP Enhanced Parallel Port (EPP) –Introduced in 1991 to increase the parallel port communication speed to 500K Bps Extended Capability Port (ECP) –Introduced further refinement to the EPP –For better performance under a multitasking environment –Introduced through a joint effort between Microsoft and HP

65. Support for EPP and ECP Must be built into the hardware namely into the motherboard Activated at the system level by enabling the support for EPP and ECP in the system BIOS For example, the System BIOS can be accessed during boot-up by pressing the delete key immediately after switching on the power to the computer

66. Other Features Supported Wake-up signal sent to the printer Consider the case of a newer laser printer that is attached to a microcomputer through an ECP port –Printer must also be connected to the microcomputer using a cable conforming to the IEEE specification

67. Wake Up Feature No printing activity for a predetermined period of time –Printer enters into a sleep mode –Printer does not consume power When a print job is ready for printing –Computer sends a signal to wake up the printer –The printing then proceeds thereafter

68. Salient Features of EPP and ECP EPP was introduced to increase the speed of the parallel port ECP was introduced to add further enhancements to EPP –Improve the performance under multitasking

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70. END OF MODULE END OF CHAPTER