Communication apparatus transmitting and receiving data through data bus, and method of reducing a consumed power in such

Abstract

A USB (Universal Serial Bus) communication apparatus includes: a driver circuit connected to a USB bus and configured to transmit a packet onto the USB bus for a packet transmission period which is determined based on a transmission request signal from another unit. A receiver control circuit generates a fixation request signal and a generation control signal in response to the transmission request signal. A receiver circuit connected to the USB bus generates a squelch signal showing that the packet is being transmitting onto the USB bus, and stops generating the squelch signal in response to the generation control signal. A line state signal control circuit is configured to output a specific line state signal based on the squelch signal to notify to another unit that the packet is been transmitting onto the USB bus, and to fix the specific line state signal in response to the fixation request signal.

What is claimed is: 
     
         1 . A communication apparatus transmitting and receiving data through data bus, comprising:
 a driver circuit connected to the data bus, and configured to transmit a differential signal onto the data bus for a data transmission period which is determined based on a transmission request signal;   a receiver circuit connected to the data bus, and configured to receive the differential signal onto the data bus and to generate a squelch signal based on received differential signal, and   a receiver power supply control circuit configured to generate a receiver power supply control signal based on the transmission request signal,   wherein power supply of the receiver circuit is turned off in response to the receiver power supply control signal which is output with a predetermined period behind start of the data transmission period.   
     
     
         2 . The communication apparatus according to  claim 1 , wherein the squelch signal is output in the predetermined period. 
     
     
         3 . The communication apparatus according to  claim 1 , wherein the power supply of the receiver circuit is turned on by the receiver power supply control signal responding to end of the data transmission period. 
     
     
         4 . The communication apparatus according to  claim 1 , further comprises a line state signal control circuit generating a line state signal based on the squelch signal,
 wherein the line state signal control circuit is fixed irrespective of the squelch signal while the power supply of the receiver circuit is tuned off.   
     
     
         5 . A method of reducing a consumed power amount in a communication apparatus transmitting and receiving data through data bus, the communication apparatus including a driver circuit and a receiver circuit, the method comprising:
 transmitting a differential signal from the driver circuit onto the data bus for a data transmission period which is determined based on a transmission request signal;   receiving the differential signal onto the data bus by the receiver circuit;   generating a squelch signal based on the differential signal which is received by the receiver circuit;   outputting a receiver power supply control signal based on the transmission request signal;   controlling the power supply of the receiver circuit in response to the receiver power supply control signal,   wherein the power supply of the receiver circuit is turned off in response to the receiver power supply control signal which is output with a predetermined period behind start of the data transmission period.   
     
     
         6 . The method according to  claim 4 , wherein the squelch signal is generated in the predetermined period. 
     
     
         7 . The method according to  claim 4 , wherein the power supply of the receiver circuit is turned on by the receiver power supply control signal responding to end of the data transmission period.