Communication apparatus with transmitted rate detecting function and method thereof

A communication apparatus for receiving an input signal transmitted from a remote apparatus at a first rate or a second rate, the second rate is higher than the first rate, the communication apparatus comprising:

• a receiving circuit, receiving the input signal with an initial receiving rate and sampling the input signal with a specific sample frequency to generate a sample result;
• a detecting circuit, coupled to the receiving circuit, determining an input transmitted rate of the input signal according to the sample result, and setting a receiving rate of the communication apparatus as a working rate according to the input transmitted rate;
• and
• a processing circuit, coupled to the receiving circuit, receiving the sample result;
• wherein the receiving circuit and the processing circuit are arranged to communicate with the remote apparatus according to the working rate.