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Questions and Answers
What is the primary function of the strobe control in asynchronous data transfer?
Which unit initiates the data transfer in source-initiated strobe control?
What is the disadvantage of the strobe control method?
What happens briefly after the strobe pulse is disabled in source-initiated strobe control?
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In destination-initiated strobe control, what is the role of the strobe pulse?
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What is the primary difference between source-initiated and destination-initiated strobe control?
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What difficulty in data transfer is overcome by using the hand shaking method?
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In synchronous transmission, data is sent in the form of:
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What is present in asynchronous transmission but not in synchronous transmission?
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What is the main advantage of asynchronous transmission?
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What is the purpose of the second control signal in the hand shaking method?
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Which of the following types of transmission is slow?
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Study Notes
Asynchronous Data Transfer
- Asynchronous data transfer takes place in two ways: Strobe Control and Hand Shaking.
Strobe Control
- Uses a single control line to time each transfer.
- The strobe can be activated by the source or the destination unit.
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Source Initiated Data Transfer:
- The data bus carries information from source to destination.
- The strobe signal informs the destination unit when a data word is available in the bus.
- The strobe signal is given after a brief delay, after placing the data on the data bus.
- A brief period after the strobe pulse is disabled, the source stops sending the data.
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Destination Initiated Data Transfer:
- The destination unit activates the strobe pulse, informing the source to send data.
- The source places the data on the data bus.
- The transmission is stopped briefly after the strobe pulse is removed.
- Disadvantages of strobe control:
- The source unit has no way of knowing whether the destination unit has received the data or not.
- The destination unit has no way of knowing whether the source unit has placed data on the bus or not.
Hand Shaking Method of Data Transfer
- Solves the difficulties of strobe control by using a second control signal that provides a reply to the unit that initiates the transfer.
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Source Initiated Transfer Using Hand Shaking:
- The Fig. 4.4 shows the data transfer procedure when initiated by the source.
Comparison of Synchronous and Asynchronous Data Transfer
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Synchronous Transmission:
- Transmission starts with a block header which holds a sequence of bits.
- Data is sent in the form of blocks or frames. +Present with the same clock pulse.
- Advantages: Fast, efficient use of transmission line, and no gap between data.
- Disadvantage: Costly.
-
Asynchronous Transmission:
- Uses start and stop bits preceding and following a character respectively.
- Data is sent in the form of byte or character.
- Absent with the same clock pulse.
- Advantages: Economical, and transmission line remains empty during gap in character transmission.
- Disadvantages: Slow, and there is a gap between data.
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Description
Learn about the different methods of asynchronous data transfer in computer organization, including strobe control and handshaking. Understand the concepts of source initiated and destination initiated data transfer.
