Operating a Tape Drive During and After a Transition To a Stand-By Mode

Abstract

In a tape drive during a transition to a stand-by mode, a tape is wound under control of a processor (e.g., CPU) until duration of a time interval between moments when rotational positions of the reels change decreases to a pre-determined threshold. Thereafter, in the stand-by mode, the processor switches control over the tape drive to a low-power logic circuit (e.g., PLC) and enters a power-save mode.

1 . A method of operating a tape drive having a first reel, a second reel and a tape wound on said reels, the method comprising:
 performing under control of a processor during a transition from an operational mode to a stand-by mode:
 winding the tape onto the first reel from the second reel; 
 monitoring rotational positions of the first and second reels; and 
 when duration of a time interval between changes in the rotational positions of said first and second reels becomes equal to or smaller than a pre-determined threshold, (i) terminating winding the tape, (ii) entering the stand-by mode, and (iii) switching control over the tape drive to a logic circuit; and 
   performing under control of the logic circuit during the stand-by mode:
 detecting a change in a rotational position of at least one of the first or second reels from a first position to a second position; and 
 counter-rotating said at least one of the first or second reels until the rotational position thereof is restored from the second position to the first position. 
   
   
   
       2 . The method of  claim 1 , and further comprising:
 monitoring the rotational positions of the first and second reels using sensors accessible by the processor.   
   
   
       3 . The method of  claim 2 , wherein said sensors are Hall effect sensors. 
   
   
       4 . The method of  claim 3 , and further comprising:
 monitoring said rotational positions of each of the first and second reels using at least three Hall effect sensors.   
   
   
       5 . The method of  claim 1 , and further comprising:
 after switching control over the tape drive to the logic circuit, operating the processor in a power save mode.   
   
   
       6 . The method of  claim 1 , and further comprising:
 during the transition, winding the tape at a lower speed than used during the operational mode.   
   
   
       7 . The method of  claim 1 , wherein the logic circuit is a programmable logic controller (PLC). 
   
   
       8 . A tape drive, comprising:
 a first reel;   a first plurality of sensors of a rotational position of the first reel;   a second reel;   a second plurality of sensors of a rotational position of the second reel;   at least one motor for rotating said reels;   a processor configured for controlling the at least one motor in an operational mode of the tape drive and during a transition from the operational mode to a stand-by mode of the tape drive; and   a logic circuit configured for controlling the at least one motor in the stand-by mode of the tape drive.   
   
   
       9 . The tape drive of  claim 8 , wherein the processor is further configured for operating in a power save mode for duration of the stand-by mode. 
   
   
       10 . The tape drive of  claim 8 , wherein the processor is further configured to control winding of the tape during the transition at a lower speed than during the operational mode. 
   
   
       11 . The tape drive of  claim 8 , wherein the processor is further configured for (i) disabling the logic circuit for duration of the operational mode, and (ii) enabling the logic circuit for duration of the stand-by mode. 
   
   
       12 . The tape drive of  claim 8 , wherein the logic circuit is configured for (i) detecting changes in a rotational position of at least one of the first or second reels, and (ii) counter-rotating said at least one of the first or second reels until the rotational position thereof is restored. 
   
   
       13 . The tape drive of  claim 8 , wherein each of the first and second pluralities of said sensors includes at least three sensors, each sensor accessible by the processor. 
   
   
       14 . The tape drive of  claim 13 , wherein said sensors are Hall effect sensors. 
   
   
       15 . The tape drive of  claim 8 , wherein the logic circuit is a programmable logic controller (PLC). 
   
   
       16 . A computer program product for operating a tape drive having a first reel, a second reel and a tape wound on said reels, said computer program product comprising:
 a data storage medium; and   computer program code within the data storage medium, said computer program code including instructions for performing:
 under control of a processor during a transition from an operational mode to a stand-by mode:
 winding the tape onto the first reel from the second reel; 
 monitoring rotational positions of the first and second reels; and 
 when duration of a time interval between moments when rotational positions of said reels change becomes equal to or smaller than a pre-determined threshold, (i) terminating winding the tape, (ii) entering the stand-by mode, and (iii) switching control over the tape drive to a logic circuit; and 
 
 under control of the logic circuit during the stand-by mode:
 detecting a change in a rotational position of at least one of the first or second reels; and 
 counter-rotating said at least one of the first or second reels until the rotational position thereof is restored. 
 
   
   
   
       17 . The computer storage product of  claim 16 , wherein said computer program code further includes including instructions for operating the processor in a power save mode after switching control over the tape drive to the logic circuit. 
   
   
       18 . The computer storage product of  claim 16 , wherein said computer program code further includes including instructions for winding the tape during the transition at a lower speed than used during the operational mode.