Control system job recovery after a malfunction

• US 4,521,847 A
• Filed: 09/21/1982
• Issued: 06/04/1985
• Est. Priority Date: 09/21/1982
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Baker, George E., Bunker, Keith G., Husted, Raymond R., Dumas, Glen A., Wilczek, Stephen P., Ziehm, Richard T., Place, George H. Jr.
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): MACDONALD, ALLEN R
• Application Number:
  US06/420,995
• Time in Patent Office: 987 Days
• Field of Search: 364/184, 364/200 MS File, 364/900 MS File, 364/186, 364/131, 364/132, 371/7, 371/9, 371/12, 371/29, 355/14 C
• US Class Current: 700/79
• CPC Class Codes: G03G 15/5012 Priority interrupt; Job recovery, e.g. after jamming or malfunction

Abstract

The present invention is a multiprocessor control system that allows full job recovery after a machine power down or after a malfunction or software crash or temporary power outage. In particular, essential variables such as the state and status of the machine and the programmed job at the time of the malfunction are maintained in nonvolatile memory. This information is continually updated in nonvolatile memory. Once the control system has reset and reinitialized all the control elements after a malfunction, the control restores or downloads all the relevant variables in the nonvolatile memory to the various control elements to maintain status. In another embodiment, the essential variables are maintained in RAM locations in a master processor and saved for downloading to the control elements.

Claims

1. In a multiprocessor machine control having a plurality of processors, the processors controlling the operation of a machine having a plurality of operating components cooperating with one another to produce a result, each of the processors capable of being reset upon occurrence of an abnormal condition, one of the processors maintaining status information in memory for each of the other processors, the status information being related to the control of the operating components of each of the processors, the control comprising

means to recognize an abnormal condition in a given one of the processors,

means for resetting said processor manifesting said abnormal condition, said means for resetting being interconnected to said means to recognize, and

means for downloading status information related to said given one of the processors from the memory of the processor maintaining status to said given one of the processors, the operation of said machine continuing after the resetting of the processor manifesting the abnormal condition.

2. The control of claim 1 wherein the processor maintaining status information is a master processor maintaining status for each of the other processors in selected nonvolatile memory locations.

3. The control of claim 1 wherein the processor maintaining status information is a master processor maintaining status for each of the other processors in selected RAM locations.

4. In a machine control having a plurality of control elements including a master control element with a memory, the contents of the memory storing status information relating to the control elements, reset circuitry connected to the master control element and at least one remote control element connected to the master control element, a method of recovery from a machine malfunction comprising the steps of

(1) the master control element recognizing the existence of a malfunction in a remote control element,

(2) the master control element determining the source of the malfunction in response to the recognition of the existence of a malfunction,

(3) the reset circuitry in response to the master control element initializing said remote control element without destroying the contents of the master control element memory storing status information,

(4) the master control element downloading the status information from the memory of the master control element to said remote control element, and

(5) continuing machine operation without loss of said status information.

5. The method of claim 4 wherein the memory storing status information is a nonvolatile memory.

6. The method of claim 5, wherein the machine includes a power up phase of each of the control elements including a memory, including the steps of the master control element resetting the control elements during the machine power up phase and downloading the contents of the nonvolatile memory to all of the memories of the control elements after reset.

7. The method of claim 4 wherein the memory storing status information is a random access memory and wherein the master control element includes a flag in memory, said flag set to indicate save status.

8. The method of claim 7 wherein the step of initializing the control element includes the step of the master control element of reading said flag in memory to save the contents of the RAM storing the status information.

9. The method of claim 4 wherein a portion of the memory in the master control element storing status information is associated with a particular remote control element, and each of the remote control elements include a memory, and the step of downloading the status information includes the step of downloading the status information of the master control element memory associated with a particular remote control element to the memory of said particular remote control element.

10. In a multiprocessor control system having a plurality of interconnected processors, each of the processors including a status memory, one of the processors being the master processor having a master memory with locations associated with each of the processors, the master processor including reset circuitry to reset each of the processors, a method of recovery from a system abnormality including the steps of

(1) the master processor identifying a particular processor manifesting the abnormaility,

(2) the master processor preventing the destruction of the contents of the master memory locations associated with the processor manifesting the abnormality,

(3) the reset circuitry resetting the processor manifesting the abnormality,

12. The method of claim 10 wherein the selected memory locations are nonvolatile memory locations controlled by the master processor.

11. (4) the master processor restoring the memory of the processor manifesting the abnormality with the contents of the master memory locations associated with the processor manifesting the abnormality.

13. In a machine control having a plurality of control processors including a master processor with a memory for continually storing machine status information and at least one remote processor providing coded transmissions, the master processor memory maintaining status information associated with said remote processor, a method of recovery from a machine malfunction comprising the steps of

(1) the master processor recognizing the existence of a malfunction,

(2) the master processor identifying the remote processor being the source of the malfunction through a coded transmission from the remote processor,

(3) the master processor initializing said remote processor without destroying the status information of the master processor memory,

(4) the master processor downloading the status information from the master processor memory associated with said remote processor to the remote processor after receiving the coded transmission, and

(5) continuing machine operation without loss of machine status in the remote processor.