Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
2001-09-07
2003-07-01
Kim, Hong (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S154000, C365S185330, C365S226000
Reexamination Certificate
active
06587916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microcomputer in which a programmable nonvolatile memory such as a flash memory is built, and more specifically, to a function of rewriting the nonvolatile memory.
2. Description of the Prior Art
Up to this time, a microcomputer characterized by the following was conventionally known: having dedicated hardware (H/W), that is to say, an automatic sequence circuit, which controls rewriting of content of a flash memory that is built in the microcomputer; and a CPU (central processing unit) of the microcomputer writes or sets a control command to the hardware, and thereby starts up hardware operation for rewriting. In this case, it was necessary for a user to transfer a rewriting control program having a function of issuing a command, and the like, to a built-in RAM under the control of the user. In addition, it was also necessary to inhibit interrupt on the user side (Example: M37902FGCHP produced by Mitsubishi Electric Corporation).
Because this rewriting processing was automatically performed by the hardware, the rewriting control program, which should be prepared on the user side, could be simplified to some degree. However, on the other hand, a layout area of an automatic sequence circuit was large, which resulted in high cost. Moreover, repair of the hardware was required to perform bug fixing of a rewriting sequence and to adapt the rewriting sequence to wafer process most suitably. The repair, however, could not be carried out easily.
On the other hand, there is also a case in which only a required minimum of automatic sequence circuits for rewriting control is provided. In this case, even time management, and comparison/judgment of a result, which are required for rewriting processing, are performed by software (S/W) on the user side (Examples: M37754FFCHP produced by Mitsubishi Electric Corporation, H8/3062F-ZTAT produced by Hitachi, Ltd.).
Because the quantity of the hardware is small, low-cost chips can be produced. On the other hand, the following problem arises: a load of the rewriting control software, which should be made on the user side, is heavy resulting in a long software development period.
In addition, a programmable-nonvolatile-memory device and a microcomputer using the same, are described in international application WO99/01824. The microcomputer comprises a control register for outputting a signal, which controls circuits (a sense amplifier, and a step-up circuit) relating to rewriting of an EEPROM (a nonvolatile memory) in the microcomputer. A means for rewriting the EEPROM by writing data directly from outside of the microcomputer to this control register successively is disclosed in the international application. Its object is to reduce cost by removing a rewriting control circuit.
This reference describes a control technology for writing required data from a writer, which is outside the microcomputer, to this control register. However, rewriting of the nonvolatile memory while user software is being operated is not described in this reference.
Moreover, although the reference states that a CPU of the microcomputer is capable of writing data to this control register in a “Serial I/O mode” in which a serial writer is used, there is no description other than that. There is no description of where the control software is specifically placed at the time of writing, and of how it operates.
In the EEPROM, reading is limited to a memory bit as an object to be rewritten. As a result, it is comparatively easy to manage the control software. However, practically, in the case of the microcomputer with built-in flash memory, reading cannot be performed when rewriting the flash memory that stores the control program. Therefore, the following limitations become indispensable conditions: executing by the control program on the built-in RAM; inhibiting interrupt; and the like. Management of this control software is very important for the microcomputer with built-in flash memory. In other words, in this rewriting technology of the microcomputer with built-in EEPROM, which uses the writer, rewriting of the flash memory during user software operation cannot possibly be realized.
The conventional microcomputers with built-in programmable nonvolatile memory are configured as described above. As a result, concerning the microcomputer with an automatic sequence circuit, there are problems in that a layout area is large, resulting in high cost; and a change in sequence is not easy. On the other hand, concerning the microcomputer that does not has the automatic sequence circuit, there are problems in that a load of rewriting control software on the user side is heavy, resulting in a long software development period.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems described above. An object of the present invention is to obtain a microcomputer with built-in programmable nonvolatile memory that is capable of the followings: decreasing a layout area by removing an automatic sequence circuit, and thereby aiming at low cost; facilitating a change in a rewriting sequence for bug fixing and for adapting the rewriting sequence to a wafer process most suitably; and reducing a load of user side software, and also shortening a software development period, by loading rewriting control firmware (F/W).
According to an aspect of the present invention, there is provided a microcomputer with built-in programmable nonvolatile memory, the microcomputer comprising: a nonvolatile memory for storing rewriting control firmware and user software in separate unit blocks respectively; at least four registers, which can be written or read by a CPU of the microcomputer: a command register for specifying content of rewriting control; an address register for specifying an address to be subjected to rewriting control; a data register for specifying data to be written; and a control signal register for specifying a control signal for a power-supply pump circuit in a nonvolatile memory and a memory decoder; wherein: the power-supply pump circuit and the memory decoder are controlled by associating given bits of the control signal register with control signals connected to the power-supply pump circuit and the memory decoder; and the rewriting control firmware reads a value that is set in the command register, the address register, or the data register, and rewrites a set value in the control signal register according to a sequence specified for each command corresponding to the read value, which is set in the command register, the address register, or the data register, to operate the power-supply pump circuit and the memory decoder, thereby executing rewriting processing including “erase” and “program” of the nonvolatile memory.
In this case, a unit block for storing the rewriting control firmware and a unit block for storing the user software may be configured so that addresses of both blocks are not consecutive.
In addition, the microcomputer with built-in programmable nonvolatile memory may comprise a status register that can be written or read by a CPU, wherein after completion of rewriting processing that includes “erase” and “program”, the rewriting control firmware writes a result of the execution into the status register.
Moreover, the rewriting control firmware comprises a user interface control unit for decoding at least a command that is set in the command register, and a command-execution control unit for controlling the power-supply pump circuit and the memory decoder for each specified command; and firmware of this command-execution control unit is transferred to a built-in RAM, and is executed on this RAM.
The rewriting control firmware is configured to start up as a result of a jump from the user software to a top address of the rewriting control firmware, and to return to a next instruction of the jump instruction in the user software after command execution is completed.
In the case of an “erase” command, the rewriting control firmware executes the “erase” and verifi
Ami Yasuhiro
Hongo Katsunobu
Iba Tomohisa
Kamiya Mikio
Kimura Hiroyuki
Kim Hong
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Microcomputer with built-in programmable nonvolatile memory does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microcomputer with built-in programmable nonvolatile memory, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microcomputer with built-in programmable nonvolatile memory will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3034668