The difference between the two schemes occurs within the microprocessor. Port mapped I/O uses a separate, dedicated address space and is accessed via a dedicated set of microprocessor instructions. Memory mapped I/O is mapped into the same address space as program memory and/or user memory, and is accessed in the same way. However, as far as the peripheral is concerned, both methods are really identical. The CPUs that use isolated I/O are bigger and more complex to build.Microprocessors normally use two methods to connect external devices: memory mapped or port mapped I/O. The isolated I/O technique has its own dedicated instruction set for accessing I/O devices. Therefore, isolated I/O becomes costlier compared to memory-mapped I/O. However, the control bus is different for data and memory: I/O devices and memory use the same address and data bus. The addresses of I/O devices are also referred to as ports. In the case of isolated I/O, we provide a separate address space other than a memory address space to I/O devices. Instructions used for accessing memory can be easily used for accessing I/O devices. One advantage of memory-mapped I/O is that we don’t need separate instruction sets for accessing I/O devices. Additionally, such CPUs consume less power due to reduced complexity. Therefore, building a CPU that uses memory-mapped I/O is easier and cheaper. In the case of memory-mapped I/O, all the buses are the same for both memory and I/O devices. Therefore, we reserve a part of the address space for I/O devices, which is not available for computer memory. The CPU either communicates with computer memory or some I/O devices depending on the address. The CPU treats I/O devices like computer memory. We assign some of the memory addresses to I/O devices. In memory-mapped I/O, both memory and I/O devices use the same address space. We assign an address to each I/O device for the CPU to communicate to that device using its address. There’re three types of buses required for I/O communication: address bus, data bus, and control bus. Additionally, hardware, including hard drives, graphics cards, and network cards for which transferring large amounts of data is important, uses the DMA method. DMA is an advantageous method for transferring a large amount of data as the CPU will be free while the data transfer takes place. In this method, we don’t need to involve the CPU in the process of data transfer. In the direct memory access (DMA) method, we transfer data directly between computer memory and I/O devices connected with a system. An example of a software interrupt is a signal to end a program like Microsoft Word so the CPU can speed up other programs like Microsoft Excel. I/O device generates an interrupt to the CPU when the I/O device is prepared for I/O operation to take place. Interrupt-driven I/O is a technique in which the CPU doesn’t need to wait to check if the I/O device is ready or not, unlike programmed I/O. Next, let’s talk about interrupt-driven I/O. Isolated I/O is popularly referred to as mapped or port mapped I/O. We can further divide programmed I/O into memory-mapped and isolated I/O. Therefore, programmed I/O keeps the CPU busy. The CPU controls the entire I/O operation. Additionally, a computer program running on the CPU initiates I/O operations in programmed I/O. It’s a data transmission method between the CPU and networking peripheral devices using the I/O interface. ![]() Let’s talk about the programmed I/O first. ![]() Let’s discuss each type of I/O technique briefly. ![]() There’re three types of I/O techniques: programmed I/O, interrupt-driven I/O, and direct memory access. Additionally, an I/O interface includes facilitates an interface for the CPU to communicate with I/O devices. The role of an I/O interface is to identify the address of the devices generated by the CPU. In general, the communication between the CPU and I/O devices occurs via a bus. It’s popularly known as the I/O interface. In order to work efficiently within a system driven by a processor, I/O devices need an interface. The CPU processes the data stored in memory and helps in transferring the data in an I/O operation. We store the information passed from I/O devices to the CPU in memory. We pass the information to I/O devices from the CPU. Some I/O devices act as input devices, some as output devices, while others act as both. Peripheral devices exchange information between the outer world and computer CPUs. ![]() Some of the most common peripheral devices attached to a computer are keyboards, mouses, monitors, network adapters, and printers. I/O is a term to describe communication between the outer world, including humans and a computer using peripheral devices.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |