Patent ID: 7724689

Claim:
An interface device for performing data transmission with a further device coupled to a network at any of a plurality of transmission rates that are regulated, the interface device comprising: a transmission rate control circuit configured to generate a switch signal that changes an operation speed of the interface device when the transmission rate must be switched; a clock generation circuit configured to change a frequency in response to the switch signal and generate a clock signal having the changed frequency; and a register adapted to store first information of a transmission capacity of the interface device itself, second information of a transmission rate that is presently possible, and third information of a transmission rate to be switched to next, wherein the interface device negotiates with the further device using the first, second, and third information to determine a transmission rate, and the transmission rate control circuit changes the operation speed of the interface device in accordance with the determined transmission rate, wherein the register stores information for a mode for maintaining the present transmission rate after a bus reset, which occurs after data transmission according to the determined transmission rate, or information for a mode for switching to a transmission rate enabling a minimum speed transmission operation after a bust reset, as fourth information, and wherein the fourth information is transferred to the further device from the interface device during the negotiation.