Las rosas de piedra

See also: Bus

A data-processing drunk indicates the whole of the lines of communication connecting the various components of a Ordinateur.

One distinguishes:

  • the bus system (or internal bus): it connects the Microprocesseur to the Random access memory;
  • the bus of extension (or bus of inputs/outputs): it connects the microprocessor to the connectors of inputs/outputs and the connectors of extension.

By extension, the term drunk is also employed in architectures of Logiciel S to indicate a component of software connection (see ORB, EAI, Middleware, etc): one then speaks about drunk software .

Description

The drunk are located inside same a Ordinateur and make it possible to connect the various functional parts of this computer between them. A bus which does not inter-connect that two devices is called a port.

The Information S transmitted can be the useful informations to be exchanged between the devices or of information of control making it possible to manage the state of the bus itself.

A bus is often characterized by a Fréquence and the number of bits of information which it can transmit simultaneously. When a bus can transmit more than one bit of information simultaneously one will speak about a parallel bus, if not a bus series. The frequency given is sometimes the frequency of the electrical signal on the bus, sometimes the rate of transmission of information, which can be a multiple of the frequency of the signal.

Thus a bus of 32 bits whose signal has a frequency of 33 megahertz can transmit 32×33×10 6 bits a second is 1,056×10 9 bits a second, is 132 Méga - Octet S a second. This result must still be multiplied if the rate of information is a multiple of the signal.

Technologies used to manufacture the buses are varied, conducting electric engraved on a printed circuit, cable, Fiberoptic etc

Parallel bus

Material

From a Physical point of view, this type of buses is a whole of conducting electric parallel. To each cycle of time, each driver transmits a bit.

These buses thus have a size of many drivers, and a size out of bits. The most current sizes (out of bits) are: 8,16,32,64 or more. When one speaks about the size of a bus, that means that it is about the number of information (or bits) that the bus can transmit in a cycle, not counted information of control.

Certain additional drivers are assigned to the transmission of the signals of controls of the state of the bus.

Operation

The bus is used to transmit a whole data processing size of the bus. The various bits of the bus have each one a weight different numbered from zero in N-1 where NR is the size of the bus. For example for a bus four bits one can transmit 16 different values (2 4 = 16).

The transmitter positions with the even urgent all the bits of the bus. At the adequate time the component reader will read all the bits at the same time. This adequate moment can be given by one of the signals of control which will change value to announce to the device reader which it is time to read the Donnée S on the bus.

Case of use

Reading and writing of the random access memory by a processor. Two distinct buses are used, a Data bus and a Bus of address. The adress bus is used to select the cells memories which must be read or written, the data bus being used to transmit the contents of the memory itself.

Bus series

Material

A bus series makes it possible to transmit information bit by bit. However it comprises more than one line making it possible to transmit information by the addition of possible signals of control and generally by the use of two distinct lines thus making it possible these buses to be bidirectional in order to simultaneously allow the transmission of information in the two directions.

Operation

The bus series transmitting the Given S bit by bit, it is necessary when one wants for example to transmit a word of 32 bits of sérialiser information for his transmission. The reader will have to carry out the opposite operation to rebuild the entering word of 32 bits starting from the bits.

Case of use

Some Périphériques data processing such as the mouse use a bus series. The hard drives of recent generations too.

Connection series RS-232

The word (byte) to transmit is sent bit by bit (weak weight in first) by the transmitter, towards the receiver which reconstitutes it.

The transmission speed of the transmitter must be identical at the speed of acquisition of the receiver. This speed is expressed in BAUDS (a baud corresponds to a bit/second, in our case). There exist various standardized speeds: 9600,4800,2400,1200… bauds.

The communication can be done in the two directions ( duplex ), either emission initially, then reception then ( half-duplex ), or simultaneous emission and reception ( full-duplex ).

The transmission being of the asynchronous type (not of common clock between the transmitter and the receiver), of the additional bits is essential to operation: bit of beginning of word ( start ), bit (S) of end of word ( stop ).

In addition, the possible use of a bit of parity , allows the detection of errors in the transmission.

The connections of the type EIA-422 and EIA-485 are derived from RS-232.

More…

The signals (animation Flash)

See also Drunk EIB

Bus parallel Vs series drunk

A priori the idea to use a parallel bus seems more effective: can a bus series, transmitting the bits of information one by one, be faster than a parallel bus transmitting them 32 by 32?

The parallel buses are limited in rate by technical difficulties and physics. At high frequencies of operation the parallel buses produce more electromagnetic interferences than a bus series what disturbs the quality of the electrical signals transmitted until making them unusable.

See too

Internal bonds

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