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Question : Consider a Device which operates with 20 MBPS operating speed.The device is operating on Programmed control mode of I/O and it has to transfer data of 20 B from it the data is transferred byte wise .Size of status register is 2 Bytes.total time needed to perform the data transfer is --------(microseconds)

 

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Time required in programmed I/O = time required to check status of I/O + data transfer time.

as the operating speed of the device is 20MBPS

so to transfer 20B it will take 1 microsecond . (i.e the data transfer time)

and to check the status of the I/O  i.e the flag sending time (2B flag  – 0.1 microsecond)

thus the total time required is = (1+0.1) microsecond.

i.e 1.1 microsecond

4 Comments

Yes the same thing is shown here ! 

the back-loop from the last (done) is considered as the next interrupt from the same device that’s why another flag check.

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@Pranavpurkar

I did not get it.can you please explain more or share some good resource.

thanks.

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yes you can refer this video https://youtu.be/uvCf6OWF4dI

and moreover CPU’s speed is more than that of the I/O device so the flag checking time is neglected.

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