The data or contents of the main memory that are used generally by the CPU are saved in the cache memory so that the processor can simply create that information in a shorter time. Whenever the CPU requires to create memory, it first tests the cache memory. If the data is not established in cache memory, so the CPU transfers into the main memory.Cache memory is located between the CPU and the main memory. The block diagram for a cache memory can be represented as −The concept of reducing the size of memory can be optimized by placing an even ... Read More

The main memory is the fundamental storage unit in a computer system. It is associatively large and quick memory and saves programs and information during computer operations. The technology that makes the main memory work is based on semiconductor integrated circuits.RAM is the main memory. Integrated circuit Random Access Memory (RAM) chips are applicable in two possible operating modes are as follows −Static − It consists of internal flip-flops, which store the binary information. The stored data remains solid considering power is provided to the unit. The static RAM is simple to use and has smaller read and write cycles.Dynamic ... Read More

The memory unit is an important component in any digital computer since it is required for saving programs and information. A very small computer with limited software can fulfill its intended function without the requirement for additional storage capacity.There is only not limited space in one memory unit to contain all the programs used in an ordinary computer. Further, various computer users acquire and continue to acquire huge amounts of data-processing software. It is not all acquired data that is required by the processor at an equal time. Hence, it is more cost-effective to use low-cost storage devices to distribute ... Read More

DMA represents Direct Memory Access. It is a hardware-controlled data transfer technique. An external device is used to control data transfer. The external device generates address and control signals that are required to control data transfer. External devices also allow peripheral devices to directly access memory. The external device which controls the data transfer is called the DMA controller.DMA Idle CycleWhen the system is turned on, the switches are in position A. The processor starts implementing the program until it requires to read a block of information from the disk. The disk processor transfers a sequence of commands to the ... Read More

An interrupt I/O is a process of data transfer in which an external device or a peripheral informs the CPU that it is ready for communication and requests the attention of the CPU.I/O ConfigurationThe terminals send and receive serial information. Each portion of serial data has eight bits of alphanumeric code, where the leftmost bit is continually 0. The serial data from the input register is transferred into the input register INPR. The output register OUTR can save the serial data for the printer. These two registers interact with the Accumulator (AC) in parallel and with a communication interface in ... Read More

In multilevel interrupts, more than one interrupt pin is present in the processor. Hence, interrupts can be recognized by the CPU on getting an interrupt request from some of the interrupt pins.The figure shows the multilevel interrupt system.Let us now discuss the process flow of a multilevel interrupt. When the external asynchronous input is inserted, the logic control of a multilevel interrupt is as follows −The processor completes its current instruction.The current contents of the program counter are stored in the stack.The program counter is loaded with the address of an interrupt service routine.Program execution reaches with the instruction taken ... Read More

In single level interrupts, many devices can interrupt the processor at the same time to attend to their requests. But all the devices raise requests through a single input pin of the CPU. When interrupted, the CPU must identify the device that raised the request. Once the I/O port is identified, the CPU attends to the request of I/O device and then continues to carry out the task that it was performing before being interrupted.In single-level interrupts, interrupt requests from all the devices are logically ORed and connected to the interrupt input of the processor. Hence, the interrupt request from ... Read More

In data transfer schemes, it can provide an efficient means of transmitting data between the processing unit and the I/O devices. In a computer, the data transfer happens between any of these combinations CPU and memory, CPU and I/O devices, and memory and I/O devices.A computer is interfaced with many devices of different speeds. Therefore, I/O devices may not be ready to transfer data as soon as the microprocessor issues the instruction for this purpose. Many data transfer schemes have been developed to solve this problem.Classification of Data Transfer SchemesThe data transfer schemes have been broadly classified into two categories ... Read More

The I/O interface supports a method by which data is transferred between internal storage and external I/O devices. All the peripherals connected to a computer require special communication connections for interfacing them with the CPU.I/O Bus and Interface ModulesThe I/O bus is the route used for peripheral devices to interact with the computer processor. A typical connection of the I/O bus to I/O devices is shown in the figure.The I/O bus includes data lines, address lines, and control lines. In any general-purpose computer, the magnetic disk, printer, and keyboard, and display terminal are commonly employed. Each peripheral unit has an ... Read More

ASCII represents American Standard Code for Information Interchange. It is the standard binary code used to represent alphanumeric characters. Alphanumeric characters are used for the transfer of information to and from the I/O devices and the computer. This standard helps seven bits to code 128 characters. However, there is an additional bit on the left that is always assigned 0. Therefore, there are 8 bits in total.The ASCII code consists of 34 nonprinting characters and 94 characters used for various control operations. There are 26 uppercase letters A through Z, 26 lowercase letters a through z, numerals from 0 to ... Read More