Microprocessor Systems

Microprocessor Systems

A microprocessor is a programmable chip that controls other semiconductor chips and devices. These include input and output devices, memory, and high-level language interpreters.

A minimal microprocessor contains an arithmetic logic unit and a control processing unit. The arithmetic logical unit performs mathematical and logical operations on data fetched from the memory device or register array.

Logic Units

A computer’s central processing unit uses an arithmetic logic unit (ALU) to perform arithmetic and logic operations. It consists of combinational logic circuits that process binary data to produce an output based on the inputs. Arithmetic logic operations include addition, subtraction, multiplication and division. Logical operations include bit-shifting operations such as logical AND, logical OR, logical NOT and XOR. The ALU can perform these operations in different orders based on the instructions that are sent from the CPU.

The ALU receives its inputs from CPU registers, which are small high-speed memory locations within the CPU. It can also accept inputs from external devices, such as keyboards and optical scanners. These inputs are converted into digital signals that are sent to the ALU over a bus-like electrical route.

An ALU’s basic functionality is determined by the microprocessor’s microarchitecture and instruction set, which dictates the types of arithmetic and logic operations it can carry out. Depending on the operation set, the ALU may support a variety of binary data formats and handle different representations such as integer or floating point numbers.

ALUs typically use a combination of circuits to process data, including registers, multiplexers and adders. It can also implement a variety of logical operations using logic gates. ALUs create a number of status output signals that are used to regulate program branching. These outputs can include Z (zero), C (carry) and N (negative).

Memory Units

Memory units store instructions and data for quick access by the CPU. Without them, the CPU would have to retrieve data from slower storage devices every time it needed it, which would slow down its processing speed.

Computer memory is divided into volatile and non-volatile types. Volatile memory loses its data when the power is turned off, while non-volatile memory retains its data indefinitely. AC converter ROM (Read Only Memory) is an example of non-volatile memory.

The amount of time it takes the memory to transfer a bit from the processor to the memory unit is called the memory latency. Memory bandwidth is the rate at which data can be transferred between the memory and the CPU. A higher memory bandwidth enables faster data transfers and lower memory latency, which improves system performance.

Registers are special additional memory locations where the control unit stores results of arithmetic and logical comparison operations. The control unit uses these special storage locations in the same way a cash register is used by a shop owner to temporarily hold cash received during a transaction.

The size and organization of CPU cache memory can significantly affect the efficiency of data retrieval, as it speeds up the response time of the CPU to the commands sent by its operating system. The common unit for measuring the size of files or the capacity of lower-level memory components is the kilobyte (KB). A gigabyte is equal to 1,024 kilobytes.

Addressing Units

The addressing unit handles the ways in which a processor refers to data or instructions. It also performs various addressing modes that reduce the size of an effective address.

An effective address may be referred to by an index register plus a static offset or a dynamic offset that is scaled by object size. An index register can also hold a displacement, which is an additional value added to the base address when referring to data or instructions. A displacement is useful for performing operations such as referencing structure field addresses in the C programming language.

Many microprocessors use an addressing mode where the offset between different locations within the code is computed relative to the program counter (PC-relative). This technique allows small offsets to be encoded inside the instruction word, which in turn reduces code size. This enables faster execution of conditional branch instructions and subroutine calls.

The addressing unit provides the control signals to interface external devices with the CPU and memory units. These control signals are known as the system bus, and are a bidirectional data line that sends command words to the DMA controller. It also carries the higher byte of the generated address to be latched by the addressing unit. It also carries the status word back from the DMA controller. This is an important function because it ensures that the CPU is not executing multiple programs at the same time.

Control Units

The control unit is a key component of a microprocessor that manages the flow of instructions and data between different parts of the CPU. It interprets and decodes fetched instructions, communicates with main memory, the arithmetic logic unit, and input/output devices. The control Delay Lines component unit also coordinates and directs other components to execute specific arithmetic or logical operations.

Its primary responsibilities include fetching and decoding instructions from the CPU’s memory, determining what operations need to be performed on data, and directing the execution of these instructions. It also manages the flow of instructions and data between the CPU’s internal registers and external devices.

Registers are temporary storage locations within the CPU that store operands and intermediate results for instruction processing. They enable faster access to and manipulation of data than if the same information were accessed from main memory.

The control unit also determines which instructions can be completed simultaneously and arranges them accordingly to ensure that all required parts of the computer are active at the same time. It is this process that makes it possible to perform a complex calculation in less than a microsecond, even on small personal computers. The control unit can be either hardwired or microprogrammed. The former is a hardware-physical arrangement of logic circuits that cannot be modified without changing their physical structure, while the latter uses a combination of gates and flip flops to create the necessary signals.