Patent ID: 6907492

Claim:
An interface circuit comprising: a data terminal for connecting a data line for USB signal transmission; a power source terminal for connecting a power source line for source power transmission; a switch for generating a switching signal for selecting one of a host function and a device function; control means for controlling the entire of the interface circuit according to a program and for outputting, when the switching signal is input, one of a set of data for pull-down resistor connection and data for source power supply for performing the host function and a set of data for pull-up resistor connection and data for source power reception for performing the device function; a host function circuit for performing transmission/reception of data for host function by control of the control means; a device function circuit for performing transmission/reception of data for device function by control of the control means; buffer means for performing transmission/reception of data via the data terminal; selecting means for selecting one of the host function circuit and the device function circuit on the basis of the switching signal and connecting the selected one to the buffer means; pull-down means for connecting a pull-down resistor to the data terminal on the basis of the data for pull-down resistor connection; pull-up means for connecting the pull-up resistor to the data terminal on the basis of the data for pull-up resistor connection; and power supply means for performing one of an operation for supplying source power to the power supply terminal on the basis of the data for source power supply and an operation for supplying source power received from the power supply terminal to inside of the interface circuit on the basis of the data for source power reception.