Abstract:
One embodiment of the invention is directed to a data processing system that includes an electrical detection circuit to determine whether the electrical power is going from “on” to “off,” or changing from “off” to “on;” a peripheral device, including a processor to calculate the amount of electrical energy required for the peripheral device to perform a task; a task queue for the peripheral device that can be read to find a task if the electrical power is going from “on” to “off;” and a non-volatile memory, including a task queue to store data describing the task if insufficient electrical energy remains available to the peripheral device to complete the task.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to scheduling the tasks for a peripheral device in a data processing system during a power failure, and more specifically to scheduling the completion of tasks for a peripheral device during a power failure in a data processing system and after power is restored. 
     2. Description of the Prior Art 
     In many data processing systems (e.g., computer systems, programmable electronic systems, telecommunication switching systems, control systems, and so forth) a power failure may occur while a peripheral device is performing one or more tasks scheduled for that peripheral device. 
     FIG. 1 illustrates a prior art approach for handling power failures in a data processing system  100 . Data processing system  100  includes an uninterruptible power supply (UPS)  106  that can briefly supply all the electrical power required to operate the core  102  of the data processing system and a peripheral device  104  (e.g., a printer or other I/O device). The UPS may or may not provide sufficient time for peripheral  104  to perform one or more scheduled tasks, such as printing one or more files. If the UPS does not provide sufficient time, then the tasks are not completed and are possibly deleted from the task queue for the peripheral. Furthermore, a larger data processing system requires a larger and more expensive UPS with a larger power capacity. It is often impractical to buy a UPS that can supply an entire data processing system, because the price and size of a higher capacity UPS rapidly increases for higher power capacities. 
     It would be desirable to have the capability to reliably insure that the occurrence of a power failure during the operation of a peripheral device in a data processing system will not prevent the completion of each scheduled peripheral task. It would also be desirable to provide an apparatus and method to handle power failures and the restoration of power without requiring a large and expensive UPS with the power capacity to supply power for an entire data processing system. 
     SUMMARY OF THE INVENTION 
     The invention provides the capability to help insure that the occurrence of a power failure during the operation of a peripheral device in a data processing system will not prevent the completion of each scheduled peripheral task. 
     The invention also provides an apparatus and method to handle power failures and the restoration of power without requiring a large and very expensive uninterruptible power supply with the capacity to supply power for an entire data processing system. 
     A first aspect of the invention is directed to a method to handle a power failure during the performance of a task by a peripheral device, wherein the peripheral device receives electrical power with an “on” state and an “off” state from a power supply, and the peripheral device is part of a data processing system which also contains a non-volatile memory. The method includes monitoring the power supply to determine whether the electrical power is changing from the “on” state to the “off” state, or changing from the “off” state to the “on” state; if the electrical power is changing from the “on” state to the “off” state, examining a first task queue for the peripheral device to find at least one task for the peripheral device in the first task queue; calculating the amount of electrical energy required for the task; performing the task if sufficient electrical energy remains available to the peripheral device to complete the task; and storing data describing the task in a second task queue in the non-volatile memory if insufficient electrical energy remains available to the peripheral device to complete the task. 
     A second aspect of the invention is directed to a data processing system that handles power failures when receiving electrical power with an “on” state and an “off” state from a power supply. The data processing system includes an electrical detection circuit for monitoring the power supply to determine whether the electrical power is changing from the “on” state to the “off” state, or changing from the “off” state to the “on” state; a peripheral device, including a processor to calculate the amount of electrical energy required for the peripheral device to perform a task; a first task queue for the peripheral device that can be read to find a task for the peripheral device if the electrical power is changing from the “on” state to the “off” state; and a non-volatile memory, including a second task queue for said peripheral device that can store data describing said task if insufficient electrical energy remains available to said peripheral device to complete said at least one task. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a prior art approach for handling power failures in a data processing system. 
     FIG. 2 illustrates one preferred embodiment of the invention for handling power failures in a data processing system. 
     FIG. 3 illustrates an alternative preferred embodiment of the invention for handling power failures in a data processing system. 
     FIG. 4 illustrates an alternative preferred embodiment of the invention shown in FIG. 3 for handling power failures in a data processing system. 
     FIG. 5 illustrates an alternative preferred embodiment of the invention shown in FIG. 4 for handling power failures in a data processing system. 
     FIG. 6 shows one flow chart for a power failure handling data processing system in accordance with the most preferred embodiment of the present invention. 
     FIG. 7 shows another flow chart for an alternative embodiment of the invention, where the energy requirement for each task of a peripheral device is calculated and stored in the task queue as the task is originally entered. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention provides an apparatus and method for handling a power failure in a data processing system. This invention can be applied to ensuring that peripheral device tasks are either performed by the peripheral device during the power failure, or saved in non-volatile memory so that the task is completely performed by the peripheral device after power is restored to the data processing system and peripheral device. 
     In preferred embodiments of the invention, there is an electrical power detection circuit to monitor the power supply of the data processing system. In the more preferred embodiments, the electrical power detection circuit is in an uninterruptible power supply (UPS). In the most preferred embodiment, the UPS is inside the peripheral device that needs it (e.g., a printer or other I/O device). In alternative embodiments, there is a UPS externally connected to a peripheral device and the non-volatile memory. The most preferred embodiment of the invention uses a disk memory to provide the non-volatile memory to store the required information for a peripheral to perform a task. The task information for a peripheral, such as a printer, can be stored in Printer Description Language (PDL), a standardized file format (e.g., TIFF, JPEG, and so forth), or a hardware-specific data format the peripheral understands. 
     Preferred embodiments of the invention use a processor in the peripheral device to calculate how much electrical energy is needed for each of set of tasks in a task queue for the peripheral device. In preferred embodiments of the invention, the electrical energy requirements for each task are calculated after a power failure is originally detected, while there is still enough electrical power available to the peripheral device to perform tasks. The calculation for a peripheral can be as simple as an estimate of the energy needed to output one page multiplied by the number of pages of output. 
     FIG. 2 illustrates one preferred embodiment of the invention for handling power failures in a data processing system  200 . The UPS  202  and the electrical power detection circuit  204  within the UPS  202  reside inside the peripheral device  206 . In one preferred embodiment of the invention, the volatile task queue  208  and the non-volatile memory  210  that contains the non-volatile memory task queue  212  reside inside the peripheral device  206 . The memory cells in the volatile task queue for the peripheral device are typically implemented with flip-flops, latches, or random access memory. The memory cells in the non-volatile memory task queue  212  for the peripheral device  206  can be implemented with disk memory, magneto-optic memory, programmable memory, such as flash memory, or a battery-supported memory. 
     FIG. 3 illustrates an alternative preferred embodiment of the invention for handling power failures in a data processing system  300 . The UPS  202  and the electrical power detection circuit  204  within the UPS  202  reside inside the peripheral device  306 . The volatile task queue  208  resides inside the peripheral device  306 . The non-volatile memory (e.g., disk memory, flash memory)  210  that contains the non-volatile memory task queue  212  resides outside the peripheral device  306 . 
     FIG. 4 illustrates an alternative preferred embodiment of the invention shown in FIG. 3 for handling power failures in a data processing system  400 . The UPS  202  and the electrical power detection circuit  204  within the UPS  202  are outside the peripheral device  406 , which contains an interface  404  to the UPS  202 . In this embodiment of the invention, the volatile task queue  208  and the non-volatile memory  210  (e.g., disk memory, flash memory) that contains the non-volatile memory task queue  212  reside inside the peripheral device  406 . 
     FIG. 5 illustrates an alternative preferred embodiment of the invention shown in FIG. 4 for handling power failures in a data processing system  500 . The UPS  202  and the electrical power detection circuit  204  within the UPS  202  are outside the peripheral device  506 , which contains an interface  404  to the UPS  202 . In this embodiment of the invention, the volatile task queue  208  resides inside the peripheral device  506 . The non-volatile memory (e.g., disk memory, flash memory)  210  that contains the non-volatile memory task queue  212  resides outside the peripheral device  506 . 
     FIG. 6 shows one flow chart  600  for a power failure handling data processing system in accordance with the most preferred embodiment of the present invention. The method starts in operation  602 , which is followed by operation  604 . In operation  604 , the power state is tested to determine if the power is starting to fail. If the power is fail, then operation  606  is next, where a test is performed to determine if there is enough energy for the peripheral device to perform all the tasks in the task queue (e.g., print out files). If the test in operation  606  determines that there is enough electrical energy to perform all the tasks in the task queue, then the tasks are performed in operation  616 . However, if the test in operation  606  determines there is not enough electrical energy for the tasks, then operation  608  is next, where all the information required for performing the tasks is saved in a non-volatile memory (e.g., a disk memory, a magneto-optical memory, a battery-supported memory, or programmable memory, such as flash memory). Then the remaining shutdown procedures are performed. Then the peripheral device waits for power. In operation  610 , when power returns, a test determines if power is returning after a power failure. If the test of operation  610  determines that there was no preceding failure, then operation  616  is next, where the tasks in the task queue are performed normally. However, if the test in operation  610  determines that the power is returning after a power failure, then operation  612  is next, where a test is performed to determine if there is a task for the peripheral device stored in the non-volatile memory. If the test in operation  612  determines there are no tasks stored in the non-volatile memory for the peripheral device, then in operation  616 , the tasks in the task queue are performed. However, if the test in operation  612  determines that there is a task for the peripheral device stored in the non-volatile memory, then in operation  614  the information for the task is retrieved from the non-volatile memory and transferred to the task queue for the peripheral device. Operation  612  then follows operation  614 , where a test is made to determine if another task remains in the non-volatile memory task queue for the peripheral device. If there is another task remaining in the non-volatile memory, then operation  614  is repeated. If there is no other task remaining in the non-volatile memory, then operation  616  is next, where the peripheral device performs each of the tasks in the task queue. The method then returns to operation  604  to test the power. 
     FIG. 7 shows another flow chart  700  for an alternative embodiment of the invention, where the energy requirement for each task of a peripheral device is calculated and stored in the task queue as the task is originally entered. Either a peripheral device processor or the main processor can calculate the electrical energy required for a task assigned to the peripheral device. The method starts in operation  702 . Operation  708  is next, where the power supply is monitored for power failure or power restoration. Operation  710  is next, where the power state is tested to determine if the power is starting to fail. If the test of operation  710  determines the power is not starting to fail, then operation  720  is next, where a test is performed to determine if the power is returning after a power failure. However, if the test of operation  710  determines that the power is starting to fail, then operation  712  is next, where a test is performed to check whether the task energy for each task in the task queue of the peripheral device was calculated before the power failure started. If the test of operation  712  determines that one or more tasks in the task queue need an energy calculation, then operation  714  is next, where the energy is calculated for the tasks in the task queue. If the test of operation  712  determines that the tasks in the task queue have their energy requirements calculated, then operation  716  is next. In operation  716  a test is performed to determine if there is enough energy for the peripheral device to perform a task (e.g., print out a file). If the test of operation  716  finds a task that can be performed before the peripheral device fails, then operation  724  is next, where that task is performed. If the test of operation  716  determines that there is not enough electrical energy for a task, then operation  718  is next, where all the information required for performing each remaining task is saved in a non-volatile memory (e.g., a disk memory, a battery-supported memory, or a flash memory). In operation  718 , after all the tasks are saved in a task backup memory, the shutdown of the peripheral is performed. In operation  720 , when power returns, a test is made to determine whether the power is returning after a power failure. If the test of operation  720  determines that there was no preceding power failure, then operation  730  is next, where each task in the task queue is performed normally. Then operation  708  is next, where the power is monitored. However, if the test of operation  720  determines that the power is returning after a power failure, then operation  722  is next, where the peripheral device task backup memory stored in the non-volatile memory is read for any remaining tasks. Then operation  728  is next, where the tasks found in the task backup memory are reloaded into the task queue for the peripheral device. Operation  730  is next, where each task in the task queue of the peripheral device is performed. The method then returns to operation  708 , where the power supply is monitored. 
     One preferred embodiment uses a UPS inside the peripheral device to supply some time for performing one or more tasks during a power failure. Other preferred embodiments use an external UPS to supply electrical power to the peripheral device and to a disk drive to store the information for tasks too large to be performed by the electrical energy available to the peripheral device. If the disk memory is external to the peripheral device, preferably an external UPS supplies power to the disk memory. Other embodiments of the invention could be implemented with one UPS for the peripheral device and another UPS for the disk memory. Other embodiments could be implemented without a UPS, and depend only the electrical energy contained in the reactive impedance of the data processing system. 
     The exemplary embodiments described herein are for purposes of illustration and are not intended to be limiting. Therefore, those skilled in the art will recognize that other embodiments could be practiced without departing from the scope and spirit of the claims set forth below.