CPU Components
CPU components refer to the essential parts of a central processing unit (CPU) in a computer. These components include the arithmetic logic unit (ALU) for performing mathematical and logical operations, the control unit for managing the execution of instructions, and the registers for temporarily storing data and instructions. Together, these components form the core processing unit of a computer system.
7 Key excerpts on "CPU Components"
eBook - ePubSemiconductor Basics
A Qualitative, Non-mathematical Explanation of How Semiconductors Work and How They are Used
- George Domingo(Author)
- 2020(Publication Date)
- Wiley(Publisher)
...and all of them share the same memories and registers. The address is what tells the computer where the desired content of the memory is located. Buffer memories are temporary memories used to store data or information on the way from one location to another. Sometimes the information comes in faster than it goes out. The buffers hold data when it flows in and out at different rates. 14.1.4 The Central Processing Unit As I show in Figure 14.1, the CPU consists mainly of three components: the control unit, the ALU, and the registers. The CPU tells every other part of the computer what to do and when to do it. The instructions for the control unit are also stored in some portion of the memory but the control unit tells the memory what instructions to look at. If you want to add two numbers, for example, the control unit goes to the right memory location and requests that the two numbers go to the desired register(s) in the ALU. It tells the arithmetic unit to pick the numbers from such and such a location in the register, add them, and send the result to a location in another register. At some point it directs that information to the output unit and displays the result in any one of the output devices. These are the four elements of an instruction: DO THIS – operational code, also known as opcode TO THIS – operant in such and such a location PUT IT THERE – location address of the result GO TO NEXT – when you finish. Figure 14.3 Symbol for the ALU. Finally, the most obvious component of the computer is the ALU. I show the symbol for the ALU in Figure 14.3. The ALU has two (or more) inputs. Let's say, for example, that input a is a 2 and input b is a 3. The command input maybe the “add” instruction, and the output is the result, the number 5. All of these, obviously, are in digital notation. The ALU has added the two numbers...
eBook - ePubElectronics Explained
The New Systems Approach to Learning Electronics
- Louis E. Frenzel(Author)
- 2010(Publication Date)
- Newnes(Publisher)
...This is called the fetch-execute cycle, which is repeated on each instruction until the program runs to completion. The execution of each instruction may call for accessing one or more data words in the memory or storing a data word in memory. The ALU is the section of the computer that carries out many of the functions that are specified by the instructions. In other words, the ALU actually processes the data. Specifically, the ALU carries out two main types of processing: arithmetic operations (such as addition, subtraction, multiplication, and division) or logic operations (such as AND, OR, complement, or exclusive OR). For example, if an add instruction is stored in memory, the control section will fetch it, interpret it, and send signals to the ALU that cause two numbers to be added. The ALU also performs data movement operations. It can move data or instruction words from one place to another inside the CPU or it can carry out memory read/write or input/output operations. These are called load and store instructions. A key part of the CPU associated with the ALU is the registers. Most ALUs have two or more registers. High-powered CPUs may have a group of 16 or more registers, called general-purpose registers (GPRs). The registers are used to temporarily store the data being processed by the ALU and the results of the computations. Other registers in the CPU store a number called an address where the data or instructions are stored, store the instruction being executed, or act as a stop-off place for data into or out of the CPU. The control section, ALU, and the registers in all micros are very closely related. They operate together and are always considered as a single unit. As indicated earlier, the combination of the control and the ALU sections is called the CPU (see Figure 6.4). In addition, microprocessors are single-chip CPUs. Besides being called CPUs, microprocessors are sometimes called MPUs or microprocessing units...
eBook - ePub- David Johnson(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...4 The Central Processing Unit Although referred to as the brain of the system, the Central Processing Unit in a normal installation is the unsung hero, buried in a control cabinet, all but forgotten. 4.1 BASIC FUNCTIONALITY In a programmable controller system, the central processing unit (CPU) provides both the heart and the brain required for successful and timely control execution. It rapidly and efficiently scans all of the system inputs, examines and solves the application logic, and updates all of the system outputs. In addition, it also gives itself a checkup each scan to ensure that its structure is still intact. In this chapter we will examine the central processing unit as it relates to the entire system. Included will be the various functional blocks in the CPU, typical scan techniques, I/O interface and memory uses, power supplies, and system diagnostics. 4.2 TYPICAL FUNCTION BLOCK INTERACTIONS In practice, the central processing unit can vary in its architecture, but consists of the basic building block structure illustrated in Figure 4.1. The processor section consists of one or more microprocessors and their associated circuitry. While it is true that some of the older generation programmable controllers were designed without the luxury of using microprocessors, most modern systems use either a single microprocessor such as the 8086 or Z-80, or multiple microprocessors such as the AMD2903, used in a bit slice architecture. This multi-tasking approach is used in the multiple microprocessor system to break the control system tasks into many small components which can be executed in parallel. The result of this approach is to achieve execution speeds that are orders of magnitude faster than their single-tasking counterparts...
eBook - ePub- Wai-Kai Chen, Wai-Kai Chen(Authors)
- 2003(Publication Date)
- CRC Press(Publisher)
...A popular approach is to divide a system into four subsystems: the central processor, the memory subsystem, the input/output (I/O) subsystem, and the system interconnection. Figure 11.1 shows the connection between these subsystems. The main components and characteristics of these subsystems will be described. 11.3.1 Central Processor A modern microprocessor’s central processor system can typically be further divided into control, data path, pipelining, and branch prediction hardware. FIGURE 11.1 Architecture subsystems of a computer system. Control Unit The control unit of a microprocessor generates the control signals to orchestrate the activities in the data path. There are two major types of communication lines between the control unit and the data path: the control lines and the condition lines. The control lines deliver the control signals from the control unit to the data path. Different signal values on these lines trigger different actions in the data path. The condition lines carry the status of the execution from data path to the control unit. These lines are needed to test conditions involving th registers in the data path in order to make future control decisions. Note that the decision is made in the control unit but the registers are in the data path. Therefore, the conditions regarding the register contents are formed in the data path and then shipped to the control unit for decision making. A control unit can be implemented with hardwiring, microprogramming, or a combination of both. In a hardwired design, each control unit is viewed as an ordinary sequential circuit. The design goals are to minimize the component count and to maximize the operation speed. The finite state machine is realized with registers, logic, and wires. Once constructed, the design can be changed only through physically rewiring the unit...
eBook - ePub- J S Anderson(Author)
- 2012(Publication Date)
- Routledge(Publisher)
...The 6502 CPU has three general purpose registers: an accumulator and two index registers, X and Y. Figure 3.2 The Z80 central processing unit Figure 3.3 The 6502 central processing unit The flag register is called the processor status register and the stack register is 8 bits wide. Otherwise, as far as registers are concerned, the 6502 is very similar to the Z80. Since it has more registers, we use the Z80 as an example to describe the internal architecture of the CPU. 1 The instruction register and CPU control The program stored in the computer RAM memory store consists of instructions and data carefully interleaved. We shall look at this in much greater detail later when we analyse the ‘fetch-execute’ sequence. For the present, suffice it to say that the CPU must look into the memory and fetch in the instructions and data and then act upon them according to carefully defined procedures. As each instruction is fetched from memory, it is placed in the instruction register and decoded. The control section performs this function and then generates and supplies all of the control signals necessary to read or write data from or to the registers, control the ALU and provide all required external control signals. 2 The arithmetic and logic unit (ALU) The 8-bit arithmetic and logical instructions of the CPU are executed in the ALU. Although it is extremely complex, the ALU operates entirely on ordinary logic gates switching and changing their outputs according to the signals applied to them. Internally the ALU communicates with the registers and the external data bus on an internal data bus. The type of functions performed by the ALU include: add, subtract, logical AND, logical OR, logical EX–OR, compare, shift, increment and decrement. When the ALU performs an operation, the result is sent to the accumulator. The ALU may (and frequently does) also affect the contents of the flag register...
- Ed Lipiansky(Author)
- 2012(Publication Date)
- Wiley-IEEE Press(Publisher)
...10 A SIMPLE CPU DESIGN The design of a simplified central processing unit (CPU) is covered in this chapter. This design exemplifies a somewhat more involved and practical design than the examples studied in the previous chapter. This entire chapter basically is a huge example that shows the most important considerations when designing a simple CPU. We start defining the CPU instruction set and the machine instruction word. What the instructions do. The registers, memory, and combinational logic blocks are the components that the CPU requires to be able to execute the defined instruction set. We will also cover the design of the sequencer or control section of the machine with the details of its state diagram and circuit implementation. Finally, a system section covers some of the most important aspects, and sometimes overlooked issues of embedded system design: clocks, resets, power decoupling, and timing. The goal of this chapter is not only to cover a simple CPU but at the same time a complex enough design example that is more comprehensive than previously covered design examples. The basic approach taken is mostly bottom up. 10.1 OUR SIMPLE CPU INSTRUCTION SET This section introduces the reader to our small CPU instruction set. The instruction set is carefully picked such that various types of the most popular machine language instructions are represented. We will not categorize this design neither as a CISC or RISC example. CISC stands for Complex Instruction Set Computer and RISC stands for Reduced Instruction Set Computer. From a computer architecture point of view our design is closer to a von Neumann machine. This is an architecture that consists of a stored-program digital machine that has a central processing unit and a single separate memory unit that holds program instructions as well as data...
- Mohamed Rafiquzzaman(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...The ALU usually performs operations such as binary addition and subtraction. The 32-bit microprocessors include multiple ALUs for parallel operations and thus achieve fast speed. The control unit of the microprocessor performs instruction interpreting and sequencing. In the fetch phase, the control unit reads instructions from memory using the PC as a pointer. It then recognizes the instruction type, gets the necessary operands, and routes them to the appropriate functional units of the execution unit. Necessary signals are issued to the execution unit to perform the desired operations, and the results are routed to the specified destination. In the sequencing phase, the control unit determines the address of the next instruction to be executed and loads it into the PC. The control unit is typically designed using one of three techniques: • Hardwired control • Microprogramming • Nanoprogramming The hardwired control unit is designed by physically connecting typical components such as gates and flip-flops. Typical 32-bit RISC microprocessors such as the Intel 80960 and Motorola 88100 are designed using hardwired control. The microprogrammed control unit includes a control ROM for translating the instructions. Intel 8086 is a microprogrammed microprocessor. Nanoprogramming includes two ROMs inside the control unit. The first ROM (microROM) stores all the addresses of the second ROM (nanoROM). If the microinstructions (which is the case with the 68000/68020/68030/68040) repeat many times in a microprogram, use of two-level ROMs provides tremendous memory savings...
