Detection method of low frequency handshaking signal

1. A detection method of low frequency handshaking signal which is suitable for a detection system, wherein the detection system comprises a host device having a first receiver and a first transmitter, and a controlled device having a second receiver, a second transmitter and a clock/data recovery device, the detection method comprising the steps of:

(a) performing a first impedance calibration when the host device is activated for sending a first low frequency signal based on the first impedance calibration and performing a second impedance calibration when the controlled device is activated for sending a second low frequency signal based on the second impedance calibration;

(b) transmitting a first high frequency training signal from the host device to the second receiver of the controlled device when the first low frequency signal and the second low frequency signal are in a predetermined condition; and

(c) transmitting a second high frequency training signal from the controlled device to the first receiver of the host device wherein the frequency of the first low frequency signal and the second low frequency signal is smaller than the frequency of the first high frequency training signal and the second high frequency training signal.

2. The detection method of claim 1 , wherein the first impedance calibration is independent of the second impedance calibration during the step (a).

3. The detection method of claim 1 , during the step (a), further comprising the steps of:

(a11 performing the second impedance calibration by the second receiver when the controlled device is electrically connected to the host device and detects a power signal of the host device;

(a12) controlling the second transmitter by the controlled device for issuing the second low frequency signal to the first receiver after the second receiver completes the second impedance calibration;

(a13) performing the first impedance calibration by the first receiver after the first receiver detects the second low frequency signal; and

(a14) controlling the first transmitter by the host device for issuing the first low frequency signal to the second receiver after the first receiver completes the first impedance calibration.

4. The detection method of claim 1 , during the step (a), further comprising the steps of:

(a21) performing the first impedance calibration by the first receiver and providing a power signal by the host device when the host device is activated;

(a22) controlling the first transmitter by the host device for issuing the first low frequency signal to the second receiver after the first receiver completes the first impedance calibration;

(a23) receiving the first low frequency signal and the power signal by the controlled device, and activating the second receiver for performing the second impedance calibration by the controlled device based on one of the first low frequency signal and the power signal when the controlled device is electrically connected to the host device; and

(a24) controlling the second transmitter by the controlled device for issuing the second low frequency signal to the first receiver after the second receiver completes the second impedance calibration.

5. The detection method of claim 1 , during the step (a), further comprising the steps of:

(a31) performing the first impedance calibration by the first receiver when the host device is activated;

(a32) controlling the first transmitter by the host device for issuing the first low frequency signal to the second receiver after the first receiver completes the first impedance calibration;

(a33) performing the second impedance calibration by the second receiver when the controlled device is activated;

(a34) controlling the second transmitter by the controlled device for issuing the second low frequency signal to the first receiver after the second receiver completes the second impedance calibration; and

(a35) receiving the second low frequency signal and the first low frequency signal respectively by the host device and the controlled device when the controlled device is electrically connected to the host device.

6. The detection method of claim 1 , wherein the first low frequency signal and the second low frequency signal which are compatible to USB 3.0 protocol.

7. The detection method of claim 1 , wherein the first low frequency signal and the second low frequency signal which are compatible to PCI-E protocol.

8. The detection method of claim 1 , wherein the first low frequency signal and the second low frequency signal which are compatible to a serial encoding and decoding bus protocol.

9. The detection method of claim 1 , wherein the frequencies of the first low frequency signal and the second low frequency signal have a range from 10 MHz to 100 MHz.

10. The detection method of claim 1 , wherein the first low frequency signal and the second low frequency signal are periodical signals having low frequency, respectively.

11. The detection method of claim 1 , wherein the first high frequency training signal and the second high frequency training signal have frequencies which are greater than 1 GHz.