The method that is used to transfer information between internal storage and external I/O devices is known as I/O interface. The CPU is interfaced using special communication links by the peripherals connected to any computer system. These communication links are used to resolve the differences between CPU and peripheral. There exists special hardware components between CPU and peripherals to supervise and synchronize all the input and output transfers that are called interface units.
The binary information that is received from an external device is usually stored in the memory unit. The information that is transferred from the CPU to the external device is originated from the memory unit. CPU merely processes the information but the source and target is always the memory unit. Data transfer between CPU and the I/O devices may be done in different modes.
Data transfer to and from the peripherals may be done in any of the three possible ways
Now let’s discuss each mode one by one.
Bus Request : It is used by the DMA controller to request the CPU to relinquish the control of the buses.
Bus Grant : It is activated by the CPU to Inform the external DMA controller that the buses are in high impedance state and the requesting DMA can take control of the buses. Once the DMA has taken the control of the buses it transfers the data. This transfer can take place in many ways.
Example it can transfer using
Bus Transfer : In which a block sequence consisting of memory words is transferred in a continuous burst where the DMA controller is the master of the memory buses. This mode is needed for fast devices like magnetic disks.
Cyclic Stealing : In this DMA controller transfers one word at a time after which it must return the control of the buses to the CPU. The CPU merely delays its operation for one memory cycle to allow the direct memory I/O transfer to “steal” one memory cycle.
|1. What is an I/O interface in computer science engineering?|
|2. What is the difference between interrupt mode and DMA mode in an I/O interface?|
|3. How does interrupt mode work in an I/O interface?|
|4. What are the advantages of using DMA mode in an I/O interface?|
|5. Can an I/O interface operate in both interrupt and DMA modes simultaneously?|