Data bus
Lesson 3.4o Treadmills
Basic concepts corridor;
Log units with the runway
Operation Corridor
By studying the lesson you will
to describe the architecture of a computer system
to know the bus of a computer system
to know how units are connected in a corridor
to know how the processor communicates with memory and drives
3.4.1 Basic concepts
A computer system, as mentioned, consists essentially of the processor, memory, and peripherals. These devices need to communicate and exchange data.
A simple way to connect is that shown in Figure 3.4.1. Each device connected to all other devices that must communicate. This way a direct connection but has the disadvantage that leads to a complicated interface. Nor can easily connect any new devices that would like to add to our system.
Figure 3.4.1 Connecting a simplistic
A more flexible and effective way of connecting devices of a computer system is the parallel connection of devices via a common data highway traffic, as shown in Figure 3.4.2. The mall is called data computer system corridor.
Figure 3.4.2. Computer system architecture
The connection is based on a common corridor, has the advantage that the connecting device is quite simple and allows easy addition of new peripherals.
The disadvantage of this diagram is that only two units can communicate with each other taftochrona. If they try the same time and two other units to exchange data then we say that we have conflict data. It's like trying to move simultaneously by the same line two different signals. To avoid collision, the movement of data in the hallway, which is the common medium of communication units, controlled by the processor.
Usually it is possible to communicate only the processor with the memory or the processor to a peripheral unit. Not permitted to communicate between two regional units or with the memory. For example, to display a character on the screen by pressing a button, you must first pass the character (the code) from the keyboard and the processor then the processor always on the screen through the corridor.
As mentioned above, the common medium of communication devices with the processor called the corridor of the computational system. Of course the corridor consists of a set of parallel connector. The crowd called the strip width. Depending on the type of information these lines we can distinguish the following groups of links that are parts of a corridor.
Data bus (Data bus) called all the lines from which data is transferred. The data can be transferred from the processor, for example to a peripheral unit or vice versa. Each line can be transferred one bit at a time. An ASCII character contains 8 bit. So to be transported ASCII characters, one character at a time, a data bus with a range of 8 bit. If the data bus width was 16 bit then it could be taken two (2) ASCII characters at a time.
Corridor Address (Address bus) called all lines of which carry the information that describes and identifies the device that wants to communicate with the processor. Because the address of the processor gives the lines directed by the processor to address the corridor. Then the lines of the address through the hallway heading for peripherals and memory.
Channel system is called the set of lines that carry commands and synchronization signals of the processor and peripheral devices for the safe and rapid transfer of data. Also, read or write signals are included in this corridor.
As mentioned above strip width called the number of lines making up. The width of the corridor is important for data transfer speed of data. The more lines of data bus, the more bits to be transmitted alongside Bruno. The width of the track data in computer systems ranging from 8 to 64 bit. For example, a data bus width to 16 bit can only carry two byte simultaneously, while a data bus to 64 bit range can carry simultaneous 8 bytes.
Finally a typical size of a corridor is the speed. Speed ramp called the number of different data can be transferred in one second. For example, a runway strip width data with 32 and 10 million data speed in seconds can be transferred εκατομμύρια 10x32 = 320 bits (bit) or 40 million bytes per second.
3.4.2 Connection Units with corridor
A computer system consists of a processor, memory, input units, output and other peripherals. As mentioned these units are connected by corridors of addresses, data and control.
A processor uses the following signals are connected to the rest of the system:
Signals from the address which gives the address of the facility with which it wants to communicate.
Data signals which reads and writes data to other units.
Mark RE (Read Enable) which is activated when the CPU wants to read data.
Signal WE (Write Enable) is activated when the CPU wants to write data.
The memory of a computer system should have similar markings to those of the processor. Address signals, data and signals RE and WE.
Also the input modules must have address and data signals. An input unit can only provide data on the runway and not get data from it. So long as the control signal to the signal has only RE (Read Enable). Similarly, output units must have signs for addresses and data, including the signal WE. The output units have no signal RE, because they write data to and never read them.
Figure 3.4.3 Corridors and control signals
Figure 3.4.3 shows the direction of data and control signals (RE, WE) with associated units.
Suppose the output unit is a monitor and a keyboard input unit. And suppose you want to appear on the screen the character corresponding to the key you press on the keyboard.
The keyboard as input module provides data when selected. Suppose in our example that the address is 200 keyboard. So the processor when it wants to read from the keyboard, select the keyboard, giving the corridor a number of addresses 200. After giving the command to write data in the corridor of the signal given by RE (Read Enable). When the keyboard is already selected, mandated to provide data in a data bus, then the code of the button you just pressed appears in the data bus and then read by the processor.
Then the editor has given this to write on the screen. We assume that the screen has the address 100. The selection screen will be when the treadmill of addresses appears at 100. The screen is output device and the processor gives the data. So to send the character on screen puts the address of the runway at 100 causing the selection screen and then the character that is read from the keyboard in the corridor of the data. Finally, the signal WE (Write Enable) enables the display, which has already been selected, get the data from the same runway.
3.4.3 Operation Runway
In a computer system, one that regulates the movement of data in the hallway is the processor. So any data transfer must necessarily be involved. When to give or receive data as well as peripherals and memory arranged by signals from control and address given by the processor.
Each regional unit of a computer system must have an address with the determined. This address is the name and each regional unit must have a unique and different address.
The same goes for memory. The set of addresses is available for memory and peripherals for input and output. A memory, but because it has many places where they can store different data for a selected set of addresses. Each time the processor wants to write or read a post from this complex memory, selects the entire memory. Of course each memory has its own decoding circuitry for selecting the specific location within the memory of this band.
The input and output modules usually have an address with the selected. Of course there are regional units with more than one location or storage reading and selected from more than one address.
Each regional unit, like the memory, must have a logical address decoding circuitry. In this circuit each unit compares the address of the runway with its own address. If the address is the same, then this unit is connected to the hallway exchanging data and communicates with the processor.
In the data bus are connected and can give information or to get all the data points of the computational system. These seem to be interrelated, since all connected to the common corridor system. The transfer of data but only one device needs to send data and another just to take them. Such data shall not be affected by other units. For the solution of this problem each unit connected on the data bus must have special buffers. When a unit is not selected then with the help of the buffer unit is disconnected and does not affect the data in the corridor. While when the unit is activated, ie chosen, it is fully plugged into the hallway.
What did you learn
In a computer system's processor, memory and more units are connected in a common hallway corridor called the computer system.
The corridor consists of a computer system data from the runway, the runway and addresses the audit trail.
In a data transfer processor always takes place when reading or writing data
Each memory module has input and output addresses are a unique name.
Each unit connected to the data bus must have special buffers, as to not affect the data of the runway when it is selected.
Terminology
Corridor computer system
Range Corridor
Data bus
Corridor addresses
Corridor control
Speed ramp
Mark RE (Read Enable)
Signal WE (Write Enable)
Control knowledge
1.the computer system called corridor and what is strip width?
2.With which signals processor connects with the runway and what its use?
3.Pos can send a data input unit to a unit of output?
4.Pos selected a unit of the processor?
5.With how the units are not selected do not affect the data in the data bus?
