A
USB connection-detection circuitry and the operation method of the same are disclosed. The circuitry includes a transmitting circuit and a detecting circuit. The transmitting circuit contains a pair of differential
signal lines, a pair of pull-down resistors and a pair of pull-up resistors wherein one pull-down
resistor and one pull-up
resistor are connected to the same differential
signal line with their own individual switches. A power-related
signal supplied by a power-supply
system is received by the transmitting circuitry and transmitted through a differential signal line. Then, the power-related signal is grounded via a pull-down
resistor. The detecting circuit is utilized to detect the power-related signals, which flow through the differential lines. When a device is connected to this connection-detection circuitry with a
USB cable, the differential
signal lines of the
USB cable are connected with the differential
signal lines of this circuitry. This results in the variation of the power-related signals, which are connected to the ground through the pull-down resistors originally. Therefore, by comparing the difference of the power-related signals before and after the connection, the connection-detection circuitry is able to automatically identify the mode of the device, which connects to the circuitry.