Patent ID: 6587916
Filing Date: 2003-07-01
Classification: G06F

Abstract:
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 â€œeraseâ€  and â€œprogramâ€  of the nonvolatile memory.