Data can be exchanged directly between an I/O module and the processor.
Just as the processor can initiate a read or write with memory, specifying the address of a memory location, the processor can also read data from or write data to an I/O module.
In this latter case, the processor identifies a specific device that is controlled by a particular I/O module
In some cases, it is desirable to allow I/O exchanges to occur directly with main memory to relieve the processor of the I/O task.
In such a case, the processor grants to an I/O module the authority to read from or write to memory, so that the I/O memory transfer can occur without tying up the processor.
This operation, known as direct memory access (DMA).
Just as the processor can initiate a read or write with memory, specifying the address of a memory location, the processor can also read data from or write data to an I/O module.
In this latter case, the processor identifies a specific device that is controlled by a particular I/O module
In some cases, it is desirable to allow I/O exchanges to occur directly with main memory to relieve the processor of the I/O task.
In such a case, the processor grants to an I/O module the authority to read from or write to memory, so that the I/O memory transfer can occur without tying up the processor.
This operation, known as direct memory access (DMA).
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