MICROCOMPUTER

• US 20130290587A1
• Filed: 04/11/2013
• Published: 10/31/2013
• Est. Priority Date: 04/27/2012
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: OGINO, Tetsuya
• Granted Patent: US 9,501,434 B2
• Time in Patent Office: Days
• US Class Current: 710/269
• CPC Class Codes: G06F 13/24 using interrupt G06F13/32 takes precedence

Abstract

A rewriting area of a flash ROM stores a main program, which includes a user vector with respect to each of interrupt factors that are different from each other in respect of types. The user vector with respect to a subject interrupt factor indicates an address, which stores an interrupt processing program that is executed when the subject interrupt factor arises. This user vector is stored in a predetermined address dedicated for the subject interrupt factor. The predetermined address of the user vector is enabled to be specified by an interrupt vector or interrupt changeover program, both of which are stored in a non-rewriting area of the flash ROM. Even when an address of the interrupt processing program is changed, the changed address is enabled to be indicated by using the user vector.

Claims

1. A microcomputer comprising:

a CPU that executes selectively (i) a main program and (ii) an onboard rewriting program that executes an onboard rewriting of the main program; and

a nonvolatile memory that includes (i) a rewriting permitted area where data are enabled to be rewritten and (ii) a rewriting forbidden area where data are forbidden from being rewritten,

the rewriting permitted area storing the main program,

the rewriting forbidden area storing the onboard rewriting program,

the rewriting forbidden area further storing an interrupt vector with respect to each of a plurality of interrupt factors, the interrupt factors being different from each other,

the interrupt vector indicating an address of a branch destination when each of the plurality of interrupt factors arises,

the microcomputer further comprising;

a change section that uses the address indicated by the interrupt vector and changes a CPU-accessed address, which is an address accessed by the CPU, into either an address within the main program or an address within the onboard rewriting program according to the main program or the onboard rewriting program, whichever is executed,

wherein;

the main program includes a user vector stored in a predetermined address that is predetermined with respect to each of the plurality of interrupt factors, the user vector indicating an address which stores an interrupt processing program that is executed when each of the plurality of interrupt factors arises; and

the change section specifies the predetermined address storing the user vector when changing the CPU-accessed address into the address within the main program.

2. The microcomputer according to claim 1, wherein:

the change section includes a variable pointer,

the variable point being rewritten into a predetermined address storing a user vector with respect to a subject interrupt factor that is one of the plurality of interrupt factors by an instruction of the main program when the main program is executed,

the variable pointer being rewritten into an address within the onboard rewriting program storing an interrupt processing program that is executed when the subject interrupt factor arises by an instruction of the onboard rewriting program when the onboard rewriting program is executed; and

the interrupt vector

refers to the variable pointer with respect to the subject interrupt factor arising, and

provides the CPU-accessed address.

3. The microcomputer according to claim 2, wherein:

the variable pointer is assigned to the subject interrupt factor that is used in common by the main program and the onboard rewriting program; and

the change section further includes a fixed pointer, which is assigned to a target interrupt factor that is one of the plurality of interrupt factors used only by the main program so as to indicate a predetermined address storing a user vector with respect to the target interrupt factor, regardless of whether the main program or onboard rewriting program is executed.

4. The microcomputer according to claim 2, wherein:

the interrupt vector is assigned with a start address of the onboard rewriting program so that the onboard rewriting program is executed first when a reset arises as one of the plurality of interrupt factors;

an execution of the onboard rewriting program is thereby started when the reset arises; and

when a rewriting request of the main program is not determined during the execution of the onboard rewriting program, the onboard rewriting program branches processing by the CPU to the main program to start an execution of the main program.

5. The microcomputer according to claim 1, wherein:

the change section includes an interrupt changeover program stored in the rewriting forbidden area of the nonvolatile memory;

when one of the plurality of interrupt factors arises, the interrupt vector instructs the CPU to execute the interrupt changeover program;

the interrupt changeover program, which is executed, (i) determines whether the main program or the onboard rewriting program was executed from a position of a program counter when the one of the plurality of interrupt factors arises and (ii) acquires type information of the one of the plurality of interrupt factors arising, the type information specifying one of a plurality of types in which the interrupt factors are different from each other;

the interrupt changeover program calculates as the CPU-accessed address an address which stores the user vector with respect to an interrupt factor that is one of the plurality of interrupt factors corresponding to the acquired type information when the main program was executed; and

the interrupt changeover program calculates as the CPU-accessed address an address within the onboard rewriting program storing an interrupt processing program, which is executed when the interrupt factor corresponding the acquired type information arises, when the onboard rewriting program was executed.

6. The microcomputer according to claim 5, wherein:

with respect to a subject interruption factor that is used in common by the main program and the onboard rewriting program, the interrupt changeover program calculates either an address storing the user vector in the main program or an address within the onboard rewriting program according to either the main program or onboard rewriting program, whichever is executed; and

with respect to a target interruption factor that is used only by the main program, the interrupt changeover program calculates an address storing the user vector in the main program, regardless of whether the main program or onboard rewriting program is executed.

7. The microcomputer according to claim 5, wherein:

when a reset arises as one of the plurality of interrupt factors, processing by the CPU branches to the onboard rewriting program by the interrupt vector or the interrupt changeover program, and an execution of the onboard rewriting program is started; and

when a rewriting request of the main program is not determined during the execution of the onboard rewriting program, processing by the CPU branches to the main program by the onboard rewriting program, and an execution of the main program is started.