Chapter 2 part B stud_ver

Chapter 2 part B stud_ver - 4.1 Chapter 2 Part B Data...

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Unformatted text preview: 4.1 Chapter 2 Part B Data Communications Fundamentals 4.2 TRANSMISSION MODES TRANSMISSION MODES The transmission of binary data across a link can be The transmission of binary data across a link can be accomplished in either parallel or serial mode. In accomplished in either parallel or serial mode. In parallel mode, multiple bits are sent with each clock parallel mode, multiple bits are sent with each clock tick. In serial mode, 1 bit is sent with each clock tick. tick. In serial mode, 1 bit is sent with each clock tick. While there is only one way to send parallel data, there While there is only one way to send parallel data, there are three subclasses of serial transmission: are three subclasses of serial transmission: asynchronous, synchronous, and isochronous. asynchronous, synchronous, and isochronous. Parallel Transmission Serial Transmission 4.3 Figure 4.31 Data Transmission Modes Data Transmission Mode: Data Transmission Mode: 1. 1. Parallel mode. Parallel mode. 2. 2. Serial mode: Serial mode: i. i. Asynchronous Asynchronous ii. ii. Synchronous. Synchronous. 4.4 Figure 4.32 Parallel transmission 4.5 Figure 4.33 Serial transmission 4.6 Distinguishing Asynchronous & Synchronous Transmission Asynchronous transmission is generally used in the following two situations: i. when the rate at which characters are generated is indeterminate ii. for transmission of blocks of characters at low data rates Asynchronous suffers the disadvantages: i. use of start and stop bits for each character gives rise to inefficient use of transmission capacity Example: For 1000 characters [8 bit per character, extra 1 start & stop bit (overhead)] total number of bits = 10000. 10000 bits is actually 1250 characters, extra 250 character ii. the bit synchronisation method becomes less reliable as the bit rate increases 4.7 Distinguishing Asynchronous & Synchronous Transmission Asynchronous transmission has Start bit & Stop bit Asynchronous transmission: clock runs unsynchronised with incoming signal Synchronous transmission: clock runs synchronised with incoming signal Less overhead, faster 4.8 Synchronous Transmission The complete block of frame of data is transmitted as a contiguous bit stream with no delay between each 8 bit element Start and stop bits are not used in synchronous transmission Two general types of synchronous transmission: Character Oriented & Bit Oriented- both use same bit synchronisation methods- major difference: character & frame synchronisation 4.9 Bit Synchronisation In synchronous transmission, the receiver maintains bit synchronisation in one of two ways: i. Clock Encoding: clock information (timing i....
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This note was uploaded on 08/27/2009 for the course FET etm taught by Professor Hi during the Spring '09 term at Multimedia University, Cyberjaya.

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Chapter 2 part B stud_ver - 4.1 Chapter 2 Part B Data...

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