Lesson 3.2: Central Processing Unit
When you have completed this chapter you will:
To design the internal structure of the CPU and to explain the operation of individual departments. (The unit of the runway, the decoding unit of command and the unit of execution)
Do you know the extra parts of the unit of execution and operations. (The control unit, registers and arithmetic logic unit)
3.2.1 Introduction
The computer processes data by following step - step the commands of a program. The part of the computer that executes commands and coordinates all functions is the central processing unit (CPU).
The CPU is a complex logic circuit, designed to read instructions from memory and executes them.
Today, more CPU manufactured in the form of an integrated circuit. In the integrated circuit, which contains the CPU, and often incorporated other auxiliary circuits, which will speak to the following chapters. The integrated circuit has come to be called the CPU (processor) or microprocessor (microprocessor).
Figure 3.2.1 Integrated microprocessor 486 DX
Just feed the CPU with voltage, it will begin implementing the program by a specific address in memory, which is considered the beginning of the program. The CPU will read the first instruction from memory and then execute it. Kind will continue with the second command, so the third As already mentioned, reading an instruction from memory is the recall phase (fetch cycle) command. This phase follows the phase of implementation (execution cycle) command.
We conclude therefore that, when a computer works, the CPU continuously withdraw instructions from memory and executes them.
3.2.2 Registers
Let us recall the example of a simple calculator (Fig. 3.1.4), which add any key clash with the existing aggregate. The CPU receives data from the keyboard and performs the act of continually adding the number of press to the existing aggregate.
What are the data read by the central processing unit? Stored for edit? Which stores the result of addition?
The data read from the keyboard, the CPU saves the registers of (registers). These registers are memory locations inside the CPU, used for temporary storage and processing. Each register has a specific name that characterizes.
Figure 3.2.2: The registers of the CPU
In Figure 3.2.2 we see a four-CPU registers. The names of these registers are A, B, C and PC respectively. In the figure we see also the contents of each register. For example, the contents of register A is 1016 = 1610.
Whenever you want to perform some arithmetic or logic operation between two numbers, you must first be transferred each of the two numbers in a register of the CPU. The reason to make this transfer is that the CPU can do arithmetic or logic operations only between the data contained in the registers. The data processed by the CPU should be stored in a register of even temporarily.
The registers are divided into general purpose registers (general purpose registers - GPR) and Special Purpose Registers (special purpose registers - SPR).
The general purpose registers are used only for storage and processing of the CPU.
The special purpose registers, except for storage areas, an inherent function of the CPU. For example, a special purpose register is the program counter, PC. The meter program keeps the address of the next instruction of the program. Based on the register value is the revocation of an order from memory.
3.2.3 Architecture of CPU
H CPU is divided in different sections. Each department is responsible for a range of functions. We try to see the different sections describing the CPU to execute a command.
Figure 3.2.3: The state of the CPU
In the figure above we see that the registers A and B of the CPU stored values "2" and "10" respectively. The following command in the program, is the proliferation of registers A and B and store the result in memory location with address 1010. This command is shown in the figure as (1010) ¬ A · B, where (1010)
3.2.4 Unit Corridor (Bus Unit)
As each command, so the order of multiplication must be withdrawn first (fetch) from memory. The CPU should read from the memory contents of address 350, where the order of multiplication.
For this reason, the CPU must have a facility to communicate with memory through the corridor. This unit displays the appropriate form of electrical signals, the address 350, which is stored the command of multiplication and then reads the aisle content of this site.
This unit is called corridor. The ramp unit produces all the necessary electrical signals to the CPU to communicate through the corridor, with memory or peripherals.
Figure 3.2.4: Unit Corridor
As shown in Figure 3.2.4, to read the unit of the runway the next program instruction from memory, you must first know the address of this command. The direction, as already mentioned, is the program counter PC. After reading the contents of program counter, the unit runway shows in binary representation, with appropriate signals, the address 350 on the runway. The memory responds with the contents of this address, which is the command (1010) ¬ A, B.
As each input into a computer so each command is represented by an appropriate binary code. So each command corresponds to a binary number, which we call source code or command. The command is stored in memory and the read phase cancellation is this number. For example, when we recall the phase of the order of multiplication from memory, travels through the corridor in the code of this command from the CPU at 350.
Similarly, the CPU increases the value of program counter PC, so that he shows to the next execution is set to 351.
3.2.5 Decoding Command Unit (Instruction unit)
In the recall phase of the code is driven by the command unit to unit ramp command decoding.
This unit recognizes that this command replication. The command (1010) ¬
Figure 3.2.5: Signal Decoding Unit
In the figure we see that the decoding unit separates the command prompt on partial information contained in the mandate recalled from memory. This information is:
1.Poia operation will run. Here we have the arithmetic operation of multiplication between two registers and storing the result in a memory address. ((Diefth.) ¬ Kat1; Kat2)
2.Poioi registrars involved: Here we have the registers A, B (Kat1 = A, B = Kat2). And finally
3.Pou will go the result: Here is the address of the memory location where you saved the result. The address is 101016. (Diefth. = 1010)
This information is passed, as we shall see later in the execution unit.
3.2.6 Execution Unit (Execution Unit)
The execution unit consists of three subunits: registers, arithmetic logic unit and control unit.
Figure 3.2.6: The Execution Unit
3.2.7 Arithmetic and Logic Unit (Arithmetic and Logic Unit - ALU)
The arithmetic and logic unit is the set of circuits of the CPU performing arithmetic and logic operations between registers of the CPU.
Depending on the type of KME, the arithmitki and logic unit (ALU) can perform operations addition, subtraction, multiplication and division of integers as well as the logic operations (OR), AND (AND), NOT (NOT).
The ALU contains specific memory locations, which holds information on the outcome of operations performed, for example if the result of the operation is greater (positive) or below (negative) from scratch. These positions are called flags (flags). Each time you run an arithmetic or logic operation information for the outcome of transactions stored in the respective flags and then we were informed that the flags.
For example suppose the CPU performs the removal of 248-254. The result of this operation is the number -6, which is less than zero. The execution of this command causes the sign flag to indicate that we have a negative effect.
Figure 3.2.7: The ALU performs the removal 248-254
3.2.8 Registers (Registers)
The registers are all the storage units of KME. As shown in the figure, the KME can do arithmetic and logic operations between registers, since they are connected to the arithmetic and logic unit. In other words, the data from input modules or memory inserted into a register and then processed by the KME.
3.2.9 Control Unit (Control Unit)
The control function of arithmetic and logic unit is the control unit. The control unit receives the individual information from the command decoding unit and follows a series of steps for execution.
For example in the case of multiplication of registers A and B, the control unit will do the following steps:
Figure 3.2.9: Running
Initially, the control unit selects the two registers, A and B, under the command should be brought to the entrance of arithmetic and logic unit.
Figure 3.2.10: The completion of the execution of the order
Will activate the operation of multiplication
Finally we store the result in a temporary register. They will then give the unit ramp to write to memory location 1010.
The ramp unit writes the result in memory and thus completes the execution of the order.
Subsequently, the CPU proceeds to the next instruction execution with the same process again (recall the mandate of the position and performance of 351).
3.2.10 The CPU 8085
One of the first CPU marketed and presented significant success was the 8085 CPU of Intel.
In Figure 3.2.11, we see the internal architecture of KME 8085.
The 8085 CPU has a very simple unit corridor, consisting of some simple digital circuits (buffers, latch). The entire circuit is necessary for the proper functioning of the corridor is built into the control unit CPU. The segregation unit of the runway from the control unit, established in most modern processors.
The unit decoding the commands of the CPU 8085, consists of the command register and the decoding logic of the order.
The CPU 8085 has 7 general purpose registers, (A, B, C, D, E, H, L) and several special purpose registers (PC, SP, interim registrar, registrar orders etc). It has an arithmetic logic unit and a sophisticated control unit.
Finally we would like to emphasize that the separation of a CPU in individual units, is not unique. Older CPU does not contain all the units in which we discussed in this course, while modern CPUs contain more and more complex units.
What I learned:
What are the registers
What does the Unit Corridor
What does the Unit of Signal Decoding
What constitutes a unit of execution
What the Control Unit
What do the registers
What does the Arithmetic and Logic Unit
Terminology
Registers (Registers)
Registrars General and Special Purpose
Unit Corridor (Bus Unit)
Decoding Unit of Instruction (Instruction Decode Unit)
Arguments of the order
Unit execution (Instruction Execution Unit)
Control Unit (Control Unit)
Arithmetic and Logic Unit - ALM (Arithmetic and Logical Unit - ALU)
Flags (Flags)
Control knowledge
1.The __________ storage units are the CPU.
2.The program counter register is a _________ purpose.
3.The CPU communicates with memory and peripherals through the corridor. The unit of the CPU responsible for this communication is called __________________.
4.Kathe command after read from memory, ________ phase of the order, led the drive _________ commands.
5.The command decode unit, separates the different order of ________ and _________ unit gives the commands.
6.The execution unit is composed of ________, ________ and _________ the unit and the unit _______.
7.The __________ and _______ is done for the Arithmetic and Logic Unit. After each operation are _______ and give us updated information on the outcome of the transaction.
Match the words on the right with the words on the left column:
Arithmetic and Logic Unit
Contact the corridor
Control unit
Registers
Corridor Unit
Execution Unit
Execution of Orders
Acts
Storage Units
Steps to execute the
