Flash memory rewriting circuit for microcontroller
AssigneeOki Electric Industry Co., Ltd.
InventorNobuaki Shinmori
Life of this patent
Estimating the term…
Abstract
A flash memory rewriting circuit capable of rewriting a flash ROM without Presenting any problem from the viewpoint of security of programs. In a transfer Program storing region of the flash ROM is stored a program to activate a CPU of a microcontroller and to transfer a rewriting data from external devices to peripherals. On a mask ROM is written, in a fixed manner, a program to activate a CPU and to write the rewriting data on a region other than the flash ROM. Because the program stored in the transfer program storing region is installed by users, no on except user can read or rewrite the program.
Claims14
A flash memory rewriting circuit being integrated into a microcontroller having a CPU, a flash memory in which an operating program defining an operation of said CPU is stored and an input/output section to input and output data to and from external devices in order to rewrite, by operations of said CPU, said operating program stored in said flash memory, comprising:
- a transfer program storing region provided, within said flash memory, in a memory region other than an operating program storing region in which said operating program is stored, which stores a data transfer program to transfer a data for rewriting said operating program to said flash memory through said external devices when said data transfer program is read and executed by said CPU;
- and
- a read only memory storing a rewriting execution program to have rewriting data fed by external devices written on said operating program storing region of said flash memory when said rewriting execution program is read and executed by said CPU.
A flash memory rewriting circuit being integrated into a microcontroller having a CPU, a flash memory in which an operating program defining an operation of said CPU is stored and an input/output section to input and output data to and from external devices in order to rewrite, by operations of said CPU, said operating program stored in said flash memory, comprising:
- a rewriting program storing region provided, within said flash memory, in a memory region other than an operating program storing region in which said operating program is stored, which stores a rewriting program to read a rewriting data for rewriting of said operating program from external devices through said input/output section when said rewriting program is read and executed by said CPU;
- and
- a write controlling circuit disposed between said CPU and said flash memory to be operated in synchronization with clocks of said CPU, which receives more than one rewriting signal used to rewrite said operating program on said operating program storing region of said flash memory by the execution of said rewriting program through the use of said CPU and which rewrites said rewriting data on said operating program storing region after receiving a rewriting execution signal from said CPU and, during the execution of said rewriting, sends out a standby requesting signal to said CPU to prevent run-away of said CPU.
Dependencies are inferred from the claim text.