Method and apparatus for managing power consumption on a bus

Abstract

An information storage device ( 10 ) includes a cartridge ( 14 ) removably inserted into a cradle ( 13 ) that has a drive module ( 18 ) releasably coupled to an interface module ( 17 ). The interface module can be operatively coupled by a cable ( 12 ) to a remote system. Communications through the cable conform to an industry-standard protocol. The storage device can receive power from either the cable or an external power source ( 31 ). The interface module can detect a change in the source of its operating power during normal system operation, and ensure that this is reported through the cable.

1. An apparatus comprising a device that includes:
 a first coupling section which can detachably couple said device to a bus that includes a power line;  
 a second coupling section which can detachably couple said device to a source of power;  
 circuitry coupled to each of said first and second coupling sections, said circuitry operating in a first mode in which said circuitry draws operating power from the power line through said first coupling section when no power is being received through said second coupling section, operating in a second mode in which said circuitry draws power through said second coupling section when a power source is supplying power to said second coupling section, automatically determining which of said first and second modes said circuitry is operating in, and automatically reporting through said first coupling section which of said first and second modes said circuitry is currently operating in;  
 wherein said circuitry automatically switches from said first mode to said second mode when a power supply begins supplying power through said second coupling section during operation of said circuitry in said first mode, and automatically reports through said first coupling section that said circuitry is now operation  operating in said second mode; and  
 wherein said circuitry includes a processor which monitors whether power from a power supply is present at said second coupling section, and which causes a reset of said bus upon detecting that a power supply has just started supplying power through said second coupling section.  
 
     
     
       2. The apparatus according to  claim 1 , wherein said bus conforms to the IEEE 1394 protocol. 
     
     
       3. An apparatus comprising a device that includes:
 a first coupling section which can detachably couple said device to a bus that includes a power line;  
 a second coupling section which can detachably couple said device to a source of power;  
 circuitry coupled to each of said first and second coupling sections, said circuitry operating in a first mode in which said circuitry draws operating power from the power line through said first coupling section when no power is being received through said second coupling section, operating in a second mode in which said circuitry draws power through said second coupling section when a power source is supplying power to said second coupling section, automatically determining which of said first and second modes said circuitry is operating in, and automatically reporting through said first coupling section which of said first and second modes said circuitry is currently operating in;  
 wherein said circuitry automatically switches from said second mode to said first mode when a power supply stops supplying power through said second coupling section during operation of said circuitry in said second mode, and automatically reports through said first coupling section that said circuitry is now operating in said first mode; and  
 wherein said circuitry includes a processor which monitors whether power from a power supply is present at said second coupling section, and which causes a reset of said bus upon detecting that a power supply has just stopped supplying power through said second coupling section.  
 
     
     
       4. The apparatus according to  claim 3 , wherein said bus conforms to the IEEE 1394 protocol. 
     
     
       5. A method of operating a device having a first coupling section which can detachably couple said device to a bus that includes a power line, having second coupling section which can detachably couple said device to a source of power, and circuitry coupled to each of said first and second coupling sections, comprising the steps of;
 operating said circuitry in a selected one of a plurality of modes, including a first mode in which said circuitry draws operating power from the power line through said first coupling section when no power is being received through said second coupling section, and a second mode in which said circuitry draws power through said second coupling section when a power source is supplying power to said second coupling section;  
 automatically determining which of said first and second modes said circuitry is currently operating in;  
 automatically reporting through said first coupling section which of said first and second modes said circuitry is currently operating in,  
 automatically switching from said first mode to said second mode when a power supply beings supplying power through said second coupling section during operating in said first mode;  
 automatically reporting through said first coupling section that operation is now occurring in said second mode; and  
 monitoring whether power from a power supply is present at said second coupling section, and forcing a reset of said bus upon detecting that power supply has just started supplying power through said second coupling section.  
 
     
     
       6. The method according to  claim 5 , including the step of configuring said bus to conform to the IEEE 1394 protocol. 
     
     
       7. A method of operating a device having a first coupling section which can detachably couple said device to a bus that includes a power line, having a second coupling section which can detachably couple said device to a source of power, and circuitry coupled to each of said first and second coupling sections, comprising the steps of;
 operating said circuitry in a selected one of a plurality of modes, including a first mode in which said circuitry draws operating power from the power line through said first coupling section when no power is being received through said second coupling section, and a second mode in which said circuitry draws power through said second coupling section when a power source is supplying power to said second coupling section;  
 automatically determining which of said first and second modes said circuitry is currently operating in;  
 automatically reporting through said first coupling section which of said first and second modes said circuitry is currently operating in;  
 automatically switching from said second mode to said first mode when a power supply stops supplying power through said second coupling section during operation of said circuitry in said second mode;  
 automatically reporting through said first coupling section that that operation is now occurring in said first mode; and  
 monitoring whether power from a power supply is present at said second coupling section, and forcing a reset of said bus upon detecting that a power supply has just stopped supplying power to said second coupling section.  
 
     
     
       8. The method according to  claim 7 , including the step of configuring said bus to conform to the IEEE 1394 protocol. 
     
     
       9. A method of operating a device having a first coupling section that can detachably couple said device to a communication bus that includes a first power line, and having a second coupling section for coupling said device to a second power line, the method comprising:
 monitoring the presence of operating power on said second power line and responsively: 
 (i) operating said device by drawing operating power from said first power line if power is not present on said second power line, and,  
 (ii) operating said device by drawing operating power from said second power line if power is present on said second power line;  
   while drawing operating power from said first power line, automatically switching said device to draw operating power from said power line if said monitoring indicates that second power line has started supplying power; and    generating a reset signal to initiate the transmission of a reporting message on the bus indicating that additional power is not required from said first power line.   
     
     
       10. The method of  claim 9  wherein said monitoring is performed by a processor running a program stored in memory. 
     
     
       11. The method of  claim 10  wherein the processor senses the presence of operating power on said second power line using an interrupt routine. 
     
     
       12. The method of  claim 9  wherein the monitoring is performed by a voltage converter having a disable input connected to said second power line. 
     
     
       13. The method of  claim 9  wherein said monitoring is performed by a reset circuit. 
     
     
       14. The method of  claim 13  wherein the reset circuit detects a voltage drop from a voltage converter upon the application of power to the second power line. 
     
     
       15. The method of  claim 13  wherein the reset circuit causes the device to commence normal operation after sufficient operating power is established. 
     
     
       16. A method of operating a device having a first coupling section that can detachably couple said device to a communication bus that includes a first power line, and having a second coupling section for coupling said device to a second power line, comprising:
 monitoring said second power line for the presence of operating power and responsively: 
 (i) operating said device by drawing operating power from said first power line if power is not present on said second power line, and,  
 (ii) operating said device by drawing power from said second power line if power is present on said second power line;  
   automatically switching said device to draw operating power from said first power line if said monitoring indicates that power is no longer present on said second power line; and,    generating a reset signal to initiate the transmission of a reporting message on the bus, wherein the reporting message includes an indication that additional power is required from said first power line.   
     
     
       17. The method of  claim 16  wherein said monitoring is performed by a processor running a program stored in memory. 
     
     
       18. The method of  claim 17  wherein the processor senses the presence of operating power on the second power line using an interrupt routine. 
     
     
       19. The method of  claim 16  wherein said monitoring is performed by a reset circuit located in the device. 
     
     
       20. The method of  claim 19  wherein the reset circuit detects a voltage drop from a voltage converter upon the application of power to the second power line. 
     
     
       21. The method of  claim 19  wherein the reset circuit causes the device to commence normal operation after sufficient operating power is established. 
     
     
       22. The method of  claim 19  further comprising the step of inhibiting the reporting via said communication bus that additional power is required from said first power line when the device is operating in a power category capable of being powered using limited power from said first power line. 
     
     
       23. An apparatus comprising:
 a first coupling means to detachably couple the device to a bus that includes a power line;    a second coupling means to couple said device to a source of power;    circuit means coupled to each of said first and second coupling means, said circuit means operating in a first mode in which said circuit means draws operating power from the power line through said first coupling means if no power is being received through said second coupling means, and operating in a second mode in which said circuit means draws power through said second coupling means if a power source is supplying power to said second coupling means;      means for automatically determining which of said first and second modes said circuit means is operating in; and,      means for automatically generating a reset signal to initiate the transmission of a reporting message through said first coupling means, said reporting message including an indication of whether additional power is required for operation of said device in response to the mode that said circuit means is now operating in; and    wherein said circuit means monitors whether power from a power supply is present at said second coupling means, and wherein said circuit means automatically switches from said first mode to said second mode when the power supply begins supplying power through said second coupling means.   
     
     
       24. The apparatus of  claim 23  wherein the means for automatically determining which of said first and second modes said circuit means is operating in comprises:
 a voltage divider controlled by said power from said power supply; and,    a plurality of lines connected to said voltage divider for conveying a binary word.   
     
     
       25. The apparatus of  claim 24  wherein the means for automatically reporting comprises a PHY circuit. 
     
     
       26. The apparatus of  claim 23  wherein said circuit means comprises a voltage converter connected to said first and second coupling means, wherein the voltage converter provides power to said device obtained from said first coupling means, and said voltage converter is disabled when a power supply begins supplying power through said second coupling means. 
     
     
       27. The apparatus of  claim 26  wherein said circuit means further comprises a diode for passing current in order to provide power to said device from said second coupling means. 
     
     
       28. A computer readable storage medium, containing instructions to cause a processor within a bus communication device to execute a method comprising:
 polling an external power line that provides power to the bus communication device to determine the state of the external power line;    determining whether the external power line has changed from a logic high to a logic low; and    if the external power line has changed from a logic high to a logic low, responsively generating a reset signal to initiate the transmission of a reporting message on the bus, wherein the reporting mesage includes an indication of a power consumption category.