Hi Mohit,

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What if the data is received ok but the ok signal doesn't reached correct?
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That will be a very rare of the event.

Look at the case where no error checking is used, take the simplest RS232 without any parity. Almost always the data is transmitted correctly. (Provided the cable length and the noise has been taken care of)

Even if the two packets (the data and the confirmation) are not equal then your micro will keep on sending the same data utill the data is acknowledged as correct.

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But what if the data is sent wrong and the confirmation is also wrong matching the original data in RAM, so in such a case a wrong transmission will be acknowledged as correct ?? ....... thinking like that will never end the story.
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OR

You can send and receive back for confirmation every data packet 3 times. If in all 3 instances there is no difference, the data is 99.999999 % correct.

Such techniques will only reduce the probability very very very low ....

No one can be 100% sure. Can we ??

Simon