The method by which data is transferred from one place to another or from one device to another is called the data transmission method. Data transmission is usually via bit. The transmission process is done through bit synchronization. Based on this bit format, data transmission is mainly divided into two parts; such that-
(A) Parallel data transmission and
(B) Serial data transmission.
Parallel Data Transmission Method:
The data bit format in the data transmission Transferring parallel data from one device to another is called parallel data transmission. This method is used for data transmission between different units located at short distances. In this method, a bit of data is transferred simultaneously in a clock pulse through individual wires. 8 separate wires are used for 8-bit data transmission. This is an expensive procedure. Because in the case of ‘N’ bit data, ‘N’ wires are required.
Serial Data Transmission Method:
The data transmission in which the data format is transferred from one device to another in the serial sequence is called serial data transmission. This method is used for data transmission between two devices located at that distance. In this case, a data bit is transferred one by one in a clock pulse through the wire. In the case of 8-bit data transmission, 8 clock pulse is required.
In the case of serial data transmission, when transmitting data in bits, different methods of bit synchronization have to be used to start and end date. Synchronization between the format of the transmitted data bits and the additional bits attached to it is called bit synchronization. The data transmission method used based on bit synchronization has come to be known as the data transmission method.
The serial transmission data transmission method is divided into three parts; such that-
1. Asynchronous Transmission
2. Synchronous Transmission
3. Isochronous Transmission
The transmission method in which data is transmitted character by character is called the asynchronous data transmission method. In this case, primary storage devices are not required for data storage. This type of transmission is also called start/stop transmission. Asynchronous transmission is usually performed when one or more terminals (keyboard or keyboard monitors) are connected to the CPU. The character-to-character time interval is unequal in this transmission.
In this transmission system, as soon as the characters are pressed on the keyboard, a 7-bit character is created, with which a parity bit is added and converted to 1 byte. This 8-bit character is preceded by a start bit in front of the transmission and one or two stop bits at the end. As a result, each character is converted to 10 or 11-bit data and transmitted.
Use of asynchronous transmission:
1. Keyboard to Computer
2. Punch card reader to Computer
3. Computer to printer
4. Asynchronous transmission is used to transfer data from computer to punch card or keyboard.
Advantages of asynchronous data transmission:
1. In this way the sender can transmit data at any time and the recipient can receive it at any time.
2. No primary storage device is required.
3. This method is more useful for low data transmission.
4. The cost is comparably low.
5. Easy to maintain.
Disadvantages of asynchronous data transmission:
1. Comparely slow speed. In this case, the data is transmitted character by character.
2. It takes more time.
3. Low Skills
4. This method requires an additional start bit and stop bit.
5. The interval between character-by-character transmissions is not equal.
Synchronous data transmission:
The method by which data is transmitted in the form of blocks is called the synchronous data transmission method. This method requires a primary storage device for data transmission. Data characters are divided into blocks (also called packets) and one block is transmitted each time. Each block has at least 80 to 132 characters. The interval between each of the two blocks is at the scheduled time. At the beginning of each block. Contains header and trailer information at the end.
Use of synchronous transmission:
1. The time of data transmission from computer to computer.
2. Transfer data from one place to another.
3. Synchronous transmission methods are used to simultaneously transfer data to many computers.
Advantages of synchronous data transmission:
1. Its speed is much higher as data is transmitted in the form of bucks.
2. The efficiency is high.
3. It takes less time.
4. This method is used to transmit more data.
5. This method does not require an additional start bit and stop bit.
6 . The interval between block by block data transmission is equal.
Disadvantages of synchronous data transmission:
1. This method requires a primary storage device.
2. The cost is relatively high.
3. Maintenance is difficult.
Isochronous Data Transmission:
Isochronous Data Transmission is an improved version of Synchronous Data Transmission. It features both asynchronous and synchronous data transmission. For example, in the Isochronous system, data is transmitted block by block and the interval between them is equal. In this method, the data transmission is said to have no delay and the interval between transmissions is brought to almost zero (0).
Isochronous data transmission can be divided into two parts. such that-
1. Serial data transmission
2. Parallel data transmission
Data Transmission Mode
The direction of data flow is called data transmission mode. The data transmission mode is divided into three parts based on the direction of data flow. such that
3. Full duplex
The method by which data flows in only one direction is called Simplex. Data can be transmitted from X to Y in simplex mode. But data cannot be transmitted from Y to X.
For example, when we watch television, only data comes to us from television. We can’t send data to TV even if we want to. This is the Simplex method.
The method by which data flows from sender to recipient and from recipient to sender but not at the same time is called a half-duplex. In this case, when A sends data to B, B will only receive data but will not be able to send any data. Once A sends data, B can send data to A. This is called one-way data flow.
For example, when talking on a walkie-talkie, it is difficult to speak from one end after the other. In this case. Data flow on both sides but has to start after the end on one side. This type of method is called the Half-duplex method.
The method by which data flows in both directions at the same time is called Full duplex. In this mode any end can send data when sending data, receiving data, or receiving data. Figure P will send data towards Q while. Q will then be able to send data to P while receiving data.
For example, when talking on the telephone, both parties can talk at the same time.
The data transmission mode can be further divided into three categories based on the number of recipients and the right to receive data.
1 Unicast Mode
2. Multicast Mode
3. Broadcast Mode
The method by which only one recipient can receive data from the sender is called Unicast Mode.
For example, Here A is the sender and B is the sender. Data sent from A is only receiving B. This is called Unicast Mode.
The method by which more than one specific recipient can receive data from the sender is called Multicast Mode.
For example, Here multiple recipients from A sender are receiving B, C and E data, but D is not receiving data. So it is called Multicast Mode.
The method by which all recipients can receive data from the sender is called Broadcast Mode.
For example, Here all the recipients B, C, D, E are receiving data from A sender. So it is called Broadcast Transmission Mode.