Electronic control unit having single non-volatile memory for multiple central processing units and data retrieval method

• US 6,944,649 B1
• Filed: 11/22/2000
• Issued: 09/13/2005
• Est. Priority Date: 11/25/1999
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Suzuki, Takanao
• Primary Examiner(s): EL HADY, NABIL M
• Application Number:
  US09/717,270
• Time in Patent Office: 1,756 Days
• Field of Search: 709/200, 709/201, 709/213, 709/214, 709/215, 709/222
• US Class Current: 709/213
• CPC Class Codes: G06F 9/3824 Operand accessing
• CPC Class Codes: G06F 9/3885 using a plurality of independent parallel functional units
• CPC Class Codes: G06F 9/3891 organised in groups of units sharing resources, e.g. clusters
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

An electronic control unit for engines or vehicles has multiple CPUs and a single non-volatile memory such as an EEPROM. The CPUs are programmed to directly receive data from the EEPROM. The CPUs may be programmed to generate respective data retrieving commands when the EEPROM is not being accessed for data retrieval. In this instance, the CPUs execute respective system register initialization processing differently from each other after a start of power supply. For instance, the system register initialization processing of a first CPU is divided while the system register initialization processing of a second CPU is not divided. Alternatively, the CPUs may be programmed to generate a data retrieving command only from the first CPU and receive the retrieved data by both the first CPU and the second CPU at the same time.

Claims

1. An electronic control unit comprising:

a plurality of CPUs;

a single non-volatile memory; and

communication ports connecting the CPUs and the non-volatile memory with one another,

wherein a first one of the CPUs is programmed to (a) check whether a second one of the CPUs is accessing the non-volatile memory before accessing the non-volatile memory, (b) send to the second CPU a notification that the first CPU will access the non-volatile memory when a check result indicates that the second CPU is not accessing the non-volatile memory, and (c) stop the notification to the second CPU after completing an access to the non-volatile memory.

2. The electronic control unit as in claim 1, wherein:

the CPUs are connected through the ports; and

the first CPU is programmed to set a signal level of the port to a level indicative of its accessing when starting to access the non-volatile memory.

3. The electronic control unit as in claim 1 wherein:

the CPUs are programmed to execute respective accessing to the non-volatile memory at different time points in initialization operations executed when a power supply to the CPUs is started.

4. The electronic control unit as in claim 3, wherein:

the first CPU is programmed to execute initialization operations of system registers thereof in a divided manner thereby to differentiate the time points of its initialization operations from that of the second CPU.

5. The electronic control unit as in claim 3, wherein:

the CPUs are programmed (a) to retrieve only specified high-priority data from the non-volatile memory in their respective initialization operations, and (b) to retrieve other low-priority data from the non-volatile memory only when required after completion of initialization operations.

21. An electronic control unit as in claim 1 wherein:

the single non-volatile memory is connected to the CPUs so that data in the single non-volatile memory is commonly used by the CPUs.

6. An electronic control unit comprising:

a plurality of CPUs;

a single non-volatile memory; and

communication ports connecting the CPUs and the non-volatile memory with one another,

wherein a first one of the CPUs is programmed to transmit a data retrieving command to the non-volatile memory, and both the first CPU and a second CPU are programmed to receive at the same time the same data from the non-volatile memory retrieved in response to the data retrieving command of the first CPU thereby to share the same retrieved data.

7. The electronic control unit as in claim 6, wherein the second CPU is programmed to receive the data retrieving command from the first CPU.

8. The electronic control unit as in claim 6, wherein:

the first CPU and the second CPU are programmed to be synchronized with each other and receive the same data from the non-volatile memory after being synchronized.

9. The electronic control unit as in claim 6, wherein:

the first CPU and the second CPU are programmed to retrieve respective individual data other than the same data separately from each other after receiving the same data.

10. The electronic control unit as in claim 6, wherein:

only the first CPU is programmed to transmit the data retrieving command as a master CPU, and the second CPU is programmed to receive the data retrieving command before receiving the same data from the non-volatile memory.

22. An electronic control unit as in claim 6 wherein:

the single non-volatile memory is connected to the CPUs so that data in the single non-volatile memory is commonly used by the CPUs.

11. A data retrieving method in an electronic control unit having a first CPU, a second CPU and a single non-volatile memory, the method comprising:

generating a data retrieving command from the first CPU and notifying the second CPU that the first CPU transmits the data retrieving command to the non-volatile memory;

retrieving data from the non-volatile memory in response to the data retrieving command; and

receiving the retrieved data by at least the first CPU directly from the non-volatile memory.

12. The method as in claim 11, further comprising:

initializing a system register of the first CPU before generating the data retrieving command, the system register being associated with an access operation of the first CPU to the non-volatile memory; and

initializing other system registers of the first CPU after receiving the data from the non-volatile memory by the first CPU.

13. The method as in claim 12, further comprising:

initializing all system registers of the second CPU before generating a data retrieving command from the second CPU, so that data retrieving command from the second CPU, is delayed so that data retrieving operations of the first CPU and the second CPU occurs at different time points.

14. The method as in claim 11, further comprising:

generating a data retrieval command from the second CPU by checking that the first CPU is not accessing the non-volatile memory,

wherein the first CPU and the second CPU are capable of directly retrieving data from the non-volatile memory, respectively, independently of each other.

15. The method as in claim 14, wherein:

the first CPU and the second CPU retrieves only predetermined high-priority data from the non-volatile memory.

16. The method as in claim 11, wherein:

the data retrieving command is generated only by the first CPU; and

the retrieved data is received by both the first CPU and the second CPU at the same time.

17. The method as in claim 16, wherein:

the retrieved data is limited to data that are shared by both of the first CPU and the second CPU.

18. The method as in claim 17, further comprising:

generating individual data retrieving commands from the first CPU and the second CPU to retrieve individual data other than the data to be shared from the non-volatile memory, respectively, after the data receiving step.

19. The method as in claim 16, further comprising:

initializing system registers of the first CPU and the second CPU at the same time immediately after a start of power supply to the first CPU and the second CPU before generating the data retrieving command from the first CPU.

20. The method as in claim 19, further comprising:

generating individual data retrieving commands from the first CPU and the second CPU to retrieve individual data other than the data to be shared from the non-volatile memory, respectively, after the data receiving step.

23. A data retrieving method as in claim 11 wherein:

the single non-volatile memory is connected to the CPUs so that data in the single non-volatile memory is commonly used by the CPUs.