Input Output Interface : Data transfer modes, DMA in Computer Architecture

Input Output Interface in Computer Architecture

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Basically, In computer System Interfaces is a method used to send Information between internal system Storage and External I/O devices.  CPU used using special communication links by the peripherals connected to any computer system. All these communication links are used to resolve the differences between CPU and peripheral.Interface unit means those all Hardware Devices that are used to Communicate between CPU and peripheral devices called Interface units.

Data Transfer Modes 

The Binary Information received from outside external hardware device stored in memory unit.The binary information Transferred from CPU to outside storage device usually originated from the memory unit sometimes called Internal Memory of computer.we see in both transfer and received techniques that are used in Data transfer modes are directly target to Memory unit.These Data transfer perform in Different modes.


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There are three types of Data Transfer Modes.

1. Programmed I/O.
2. Interrupt- initiated I/O.
3. Direct memory access( DMA).

1.) Programmed I/O - -  In the Programmed I/O each data is transfer by an Instruction in the Program.It has does not any direct memory access from the CPU.Each data transfer based on the Programmed Instruction.In programmed I/O the CPU stays in the programmed loop until the Peripheral I/O device accept the Data Transfer.This is time consuming Process and Biggest disadvantages of Programmed I/O modes transfer.For overcome for this we use interrupt I/O modes transfer.we discuss this below.

2.) Interrupt-Initiated I/O - - In the above mode Programmed I/O that we  see the CPU kept busy Unnecessarily.In this method we use Interrupt driven method.So firstly we need to know what is Interrupt ? Basically, An Interrupt is a special signal or conditions that is occur for meantime.CPU executes another program or interrupt whenever it is determined that the external device is ready for data transfer.Interface monitoring the whole process.when device is ready for Data transfer that CPU stops the whole task that it was already performing.

3.) Direct Memory Access - - We see in both Data modes transfer in which CPU is used to share data between devices.But in DMA data is directly transfer between devices using directly RAM or Memory unit not CPU.The Process of using directly RAM is called DMA. But the Biggest Disadvantage of DMA is during the data transfer a meantime CPU is idle and it has no control.


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Bus request : it is used by DMA to control the request of data transfer Buses.


Bus Grant : Bus grant is used by DMA to inform external Hardware DMA Controller that are used to control of the Buses.Once DMA takes all control of Buses then data is transferred in many ways.

In Next Post we Discuss How DMA Controller works . . . . . .



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