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Programmed input–output (also programmable input/output, programmed input/output, programmed I/O, PIO) is a method of data transmission, via input/output (I/O), between a central processing unit (CPU) and a peripheral device, [1] such as a Parallel ATA storage device. Each data item transfer is initiated by an instruction in the program ...
Many of the computers were based on the First Draft of a Report on the EDVAC report published in 1945. In what became known as the Von Neumann architecture, a central control unit and arithmetic logic unit (ALU, which he called the central arithmetic part) were combined with computer memory and input and output functions to form a stored program computer. [3]
A computer with a von Neumann architecture stores program data and instruction data in the same memory, while a computer with a Harvard architecture has separate memories for storing program and data. [5] [6] However, the term stored-program computer is sometimes used as a synonym for the von Neumann architecture.
A small and fast buffer memory between the CPU and the main memory. Reduces access time for frequently accessed items (instructions / operands). cache coherency The process of keeping data in multiple caches synchronised in a multiprocessor shared memory system, also required when DMA modifies the underlying memory. cache eviction
Some devices can be "reprogrammed" if the new data replaces "1"s with "0"s. Some CPU instruction sets (e.g. 6502) took advantage of this by defining a break (BRK) instruction with the operation code of '00'. In cases where there was an incorrect instruction, it could be "reprogrammed" to a BRK causing the CPU to transfer control to a patch.
By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make digital control of more devices and processes practical. Mixed-signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems.
An embedded system on a plug-in card with processor, memory, power supply, and external interfaces. An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system.
The advantage over a hard-wired CPU is that internal CPU control becomes a specialized form of a computer program. Microcode thus transforms a complex electronic design challenge (the control of a CPU) into a less complex programming challenge. To take advantage of this, a CPU is divided into several parts: