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data bus

Standardized data exchange between computer components

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Bus (Bus) means Computer Components between Normalization To exchange data, that is, to provide the components with data transfer and control logic 。 On the other hand, if we say a main board (Mother Board) is a city, so the bus is like a city bus (bus), which can transmit back and forth non-stop operation according to the fixed driving route Bit （bit）。 These lines can only transmit one bit at a time. Therefore, multiple lines must be used at the same time to send more data. The number of data that the bus can transmit at the same time is called width. In bits, the larger the bus width, the better the transmission performance. Bus bandwidth (That is, the total number of data that can be transmitted in a unit time) is: bus bandwidth=frequency × width (Bytes/sec).

Chinese name: data bus

Foreign name: DataBus
Purpose: Used to transmit data information

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Sharing and Exchange

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DataBus. Standardized a large integrated application system homogeneous system 、 Heterogeneous system And other aspects data sharing And exchange implementation methods, and data exchange standards between systems. It can be used to transmit information between microprocessor and memory, microprocessor and I/O interface. The width of data bus is an important indicator of computer performance. The data bus of microcomputer is mostly 32 bit or 64 bit.

one Business Entity Data exchange: each Subsystem There is a business entity layer in the architecture layer, and the data exchange mechanism establishes a layer transparent to all application systems in the business entity layer. No matter what specific technical solutions are implemented between subsystems, they can be shared and interacted through the business entity layer, which also establishes that Continuous integration And business expansion, so as to realize an extensible and complete Integrated information system 。^[1]

2. WebService data exchange: Web Services Standards ， Web Services It provides a scheme for sharing and exchanging data between heterogeneous systems, and can also be used for product integration using unified interface standards data sharing And exchange.

Exchange mode

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schematic diagram

one Business Entity Layer data exchange, which is isomorphic Subsystem The most direct and efficient exchange scheme between systems. Through definition between isomorphic subsystems data object Interface layer, via DTO To transfer, or directly connect or access data tables in the database, so as to achieve data sharing and exchange between homogeneous subsystems. For example data sharing And exchange Business system And data mining.

two WebService data exchange In the case of data decentralization among heterogeneous subsystems, effective technical means must be used to ensure heterogeneous data sharing and exchange. WebService is a standard Web based service that is not subject to transport protocol Or hardware, nor the specific implementation technology of the subsystem. In addition, more advanced and complete application systems or products provide Web Service based Integration interface 。 This solves the problem of heterogeneous Subsystem Data sharing and exchange between. WebService can also solve data exchange across networks and industry systems, which requires that the other interface unit also has WebService services.

3. Format file data exchange, which is connected with External system File transmission, internal system and external information exchange requirements in business, and corresponding data sharing And exchange technology mechanism. Such problems are usually solved by file system based technical solutions, such as Document submission 、 File exchange Etc. For example, there is real-time and non real-time data exchange among tax, database and bank. This exchange optimization scheme is to use files to exchange through Socket. The implementation of such technologies generally adopts the underlying technology.

Connector

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Connector

The data bus connector (DBconnector) is used to connect serial And parallel cable to data bus connector. Data bus connector The naming format is DB-x, where x represents the number of wires in the connector. Each line is connected to a pin in the connector, but in many cases, not all pins are assigned a function. The data bus connector is EIA/TIA standard definition 。 It is a type of connector used to connect serial and parallel cables to a data bus. The DB connector is named in the format of DB-x, where x represents the number of lines in the connector. Each line is connected to the pins in the connector, but in many cases, not all pins are assigned functions. DB connectors are available in 9, 15, 25, 37 and 50 pin sizes. The DB connector defines the physical structure of the connector, not the purpose of each line. For example, DB-9 has 9 pins and is used to connect a mouse. The DB-25 has 25 pins and is used to connect a printer.

Technical indicators

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Program bus

1. Bus bandwidth (Bus data transfer rate) The bandwidth of the bus refers to the unit time Internal bus The amount of data uploaded, that is, the maximum steady state of MB transferred per note Data transmission rate 。 The two factors closely related to the bus are Bit width And bus working frequency , the relationship between them:

Bus bandwidth=bus operating frequency * bus bit width/8

2. Bit width of bus

The bit width of the bus means that the bus can transmit at the same time binary data Of digit , or the number of bits of the data bus, that is, 32-bit, 64 bit bus width concepts. The wider the bit width of the bus, the greater the data transmission rate per second bandwidth The wider.

3. Operating frequency of bus

Bus operation clock frequency with MHZ The higher the operating frequency is, the faster the bus operates, Bus bandwidth The wider.

operation

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Model

One operation process of the bus is to complete the transmission of information between two modules. The main module starts the operation process, and the other is the slave module. Only one main module can occupy the bus at a time.

Bus operation steps: main module application Bus control ， bus controller Make a decision.

data transfer Error check of: after the master module gets the bus control right addressing Slave module, data transmission is carried out after confirmation of slave module.

Bus timing protocol: Timing protocol It can ensure that both sides of data transmission operate synchronously and transmit correctly. There are three types of timing protocols:

Synchronous bus timing: all modules on the bus share the same Clock pulse Control the operation process. All actions of each module are generated in Clock cycle Most actions are completed in a clock cycle.

Asynchronous bus timing: the occurrence of the operation is determined by the specific signal of the source or destination module. The occurrence of an event on the bus depends on the occurrence of the previous event, and both parties provide contact signals to each other.

Bus timing protocol

Semi synchronous bus timing: the time interval of each operation on the bus can be different, but it must be an integral multiple of the clock cycle. The appearance, sampling and end of the signal are still Common clock Is the benchmark. ISA bus adopts this timing method.

Data transmission type: single week mode and burst mode.

Single cycle mode: one Bus cycle Only one data is transmitted.

Burst mode: transmit multiple data after obtaining the control right of the main line. addressing The first address of the destination is given when accessing the first data. The address from data 2 and 3 to data n is automatically addressed according to certain rules based on the first address (such as automatically adding 1).

standard specification

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Standard System Architecture Bus

Bus is a class The signal line The set of is a common channel for information transmission between modules. Through it, various data and commands can be transmitted between computer components. In order to make products from different suppliers interchangeable and give users more choices, bus technical specifications should be standardized.^[2]

Bus standards should be carefully considered and strictly regulated. Bus standards (technical specifications) include the following parts:

Mechanical structure specification: module size, bus plug, bus connector and installation size are uniformly specified.

Functional specification: Each signal line (pin name), function and working process of the bus shall be uniformly specified.

Electrical specification: effective level, dynamic conversion time, load capacity, etc. of each signal line of the bus.

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