Electronic apparatus in which functioning of of a microcomputer is monitored by another microcomputer to detect abnormal operation

• US 20090055685A1
• Filed: 08/20/2008
• Published: 02/26/2009
• Est. Priority Date: 08/22/2007
• Status: Active Grant

• Current Assignee: DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Mochida, Kentaro, Satoh, Yasuhiko, Kawakubo, Atsushi, Nishii, Takahito, Usami, Masayuki
• Granted Patent: US 8,091,014 B2
• Time in Patent Office: Days
• US Class Current: 714/30
• CPC Class Codes: G05B 19/0428 Safety, monitoring G05B19/0423 takes precedence
• CPC Class Codes: G05B 2219/24196 Plausibility check in channels for correct sequence or result
• CPC Class Codes: G06F 11/0739 in a data processing system embedded in automotive or aircraft systems
• CPC Class Codes: G06F 11/0751 Error or fault detection not based on redundancy power supply failures G06F1/30; network fault management H04L41/06

Abstract

In an electronic apparatus, a first microcomputer is monitored by a second microcomputer, which periodically transmits data relating to a main function to the first microcomputer to be processed. The first microcomputer periodically updates a variable value, performs a predetermined calculation operation whose final result should be a specific fixed value, adds that final result to the updated variable value to obtain a sum value, and transmits the sum value and updated variable value concurrently to the second microcomputer. The second microcomputer determines that the first microcomputer is operating abnormally if the difference between the received sum value and variable value is not equal to the specific fixed value.

Claims

1. An electronic apparatus comprising a first microcomputer and a second microcomputer coupled for communication with one another, wherein said first microcomputer is configured to repetitively execute

a first calculation procedure of successively setting predetermined bit patterns in respective registers of a CPU (central processing unit) core of said first microcomputer and executing predetermined calculation processing which utilizes said registers, said bit patterns and calculations being predetermined such that a specific fixed value is obtained as a final result from said calculations when each of said registers are functioning normally,

a second calculation procedure of updating a variable value and adding said final result to said updated variable value, to obtain a sum value, and

a transmission procedure of transmitting information expressing said sum value, and information expressing said variable value which was utilized in calculating said sum value, to said second microcomputer;

and wherein said second microcomputer is configured to execute

a subtraction procedure of operating on said information expressing said sum value and said variable value, for subtracting said variable value from said sum value to thereby obtain a subtraction value, and

a judgement procedure of judging whether or not said subtraction value is identical to said specific fixed value, and determining whether or not abnormal operation of said first microcomputer is occurring, based on results of said judgement.

2. An electronic apparatus according to claim 1, wherein said second microcomputer is configured to transmit notification of abnormal operation of said second microcomputer to an external apparatus, when said abnormal operation is detected by said judgement procedure.

3. An electronic apparatus according to claim 1, wherein:

said first microcomputer and said second microcomputer are respectively configured to periodically exchange information relating to a main function of said electronic apparatus, for operating in cooperation to execute said main function, and wherein each of said first homework calculation procedure, said second homework calculation procedure, said transmission procedure and said judgement procedure are executed periodically; and

said first microcomputer is configured to transmit currently derived information relating to said main function to said second microcomputer together with information expressing currently obtained ones of said sum value and said variable value.

4. An electronic apparatus according to claim 3, wherein said second microcomputer transmits information relating to said main function to said first microcomputer at each of a first series of time points having a fixed repetition period, and wherein said first microcomputer transmits said currently derived information relating to the main function and said information expressing said currently obtained sum value and variable value to said second microcomputer at each of a second series of time points, which are not synchronized with said first series of time points.

5. An electronic apparatus according to claim 4, wherein said first series of time points are synchronized with frame periods of a video signal, and in each of said frame periods:

said second microcomputer transmits data relating to said main function to said first microcomputer;

said first microcomputer thereafter derives currently obtained ones of said sum value and said variable value and executes processing relating to said main function based on said data received from said second microcomputer, and

on completion of said processing relating to the main function, said first microcomputer transmits information expressing said currently obtained sum value and variable value to said second microcomputer together with information expressing results of said processing relating to the main function.

6. A method of judging occurrence of abnormal operation of a first microcomputer of an electronic apparatus which comprises said first microcomputer and a second microcomputer, the method comprising:

controlling said first microcomputer to periodically update a variable value,

execute predetermined calculation processing to obtain a final calculation result, said calculation processing being predetermined to produce a specific fixed value as said final calculation result when said first microcomputer is functioning normally,

add said variable value to said final calculation result to obtain a sum value, and

concurrently transmit said sum value and said variable value to said second microcomputer;

and controlling said second microcomputer to respond to each occurrence of receiving a sum value and variable value transmitted from said first microcomputer, by

subtracting said received variable value from said received sum value to obtain a subtraction value,

comparing said subtraction value with said predetermined fixed value,

incrementing an error count value when said subtraction value differs from said predetermined fixed value, and resetting said error count value when said subtraction value is identical to said predetermined fixed value,

comparing said error count value with a predetermined maximum value, and

determining that abnormal operation of said first microcomputer is occurring, when said error count value is judged to exceed said maximum value.

7. A method of judging occurrence of abnormal operation of a first microcomputer of an electronic apparatus in which a second microcomputer periodically transmits respective data sets relating to a main function of said electronic apparatus to said first microcomputer and in which first microcomputer processes each received one of said data sets to obtain a corresponding set of processed data relating to said main function and transmits each said set of processed data to said second microcomputer upon completion of said processing, the method comprising:

controlling said first microcomputer to respond to a currently received data set that has been transmitted from said second microcomputer, by

executing said processing relating to the main function on said received data set,

updating a variable value,

executing calculation processing to obtain a final calculation result, said calculation processing being predetermined to produce a specific fixed value as said final calculation result when said first microcomputer is functioning normally,

adding said updated variable value to said final calculation result to obtain a sum value, and

concurrently transmitting said sum value and said updated variable value to said second microcomputer, together with transmitting a set of processed data corresponding to said currently received data set;

and controlling said second microcomputer to respond to receiving said sum value and variable value transmitted from said first microcomputer, by

subtracting said received variable value from said received sum value to obtain a subtraction value,

comparing said subtraction value with said predetermined fixed value,

incrementing an error count value when said subtraction value differs from said predetermined fixed value, and resetting said error count value when said subtraction value is identical to said predetermined fixed value,

comparing said error count value with a predetermined maximum value, and

determining that abnormal operation of said first microcomputer is occurring, when said error count value is judged to exceed said maximum value.