US 6,587,916 B2Granted

Microcomputer with built-in programmable nonvolatile memory

AssigneesMitsubishi Denki Kabushiki Kaisha, Mitsubishi Electric Semiconductor System Corporation, Mitsubishi Electric Engineering Company Limited

InventorsKatsunobu Hongo, Tsutomu Tanaka, Toshihiro Sezaki, Hiroyuki Kimura, Mikio Kamiya, Yasuhiro Ami, Kunio Tani, Tomohisa Iba

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Abstract

A microcomputer comprises: a flash memory for storing rewriting control F/W and user S/F; a command register for specifying content of rewriting control; a address register to be subjected to rewriting-control; a data register for specifying data to be written; a power-supply pump circuit in the flash memory; and a control signal register for specifying/outputting a control signal to a memory decoder. A CPU of the microcomputer is capable of accessing these four registers to perform writing or reading. A given bit of the control signal register corresponds to a given control signal. A value written to the register becomes a control signal that will be directly supplied to both of the power supply circuit and the memory decoder, in the flash memory, to control them. By rewriting a set value of this control signal register using the rewriting control F/W according to a specified sequence, processing such as “erase” and “program” of the flash memory is performed. As a result, a layout area of an automatic sequence circuit is decreased, and a change in a sequence is also facilitated.

Claims19

Dependent claims

A microcomputer with built-in programmable nonvolatile memory, said 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 said 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.

6 more elements

Dependencies are inferred from the claim text.