ON-BOARD REWRITING DEVICE AND EXTERNAL CLOCK INPUT CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide an on-board rewriting device which can executes a loader program fast and shorten a rewriting time by switching the execution clock of a CPU to an externally supplied high-speed clock when the on-board rewriting of a nonvolatile memory built-in microcontroller mounted on a set is performed. SOLUTION: The device comprises a rewriting mode register 18 which generates a signal when the nonvolatile memory is rewritten on the board 12, a selector 19 which switches the source clock of the CPU and UART 11 to the external clock, and a filter 20 which cuts a high-speed clock signal dedicated to rewriting which is inputted from a reset terminal; when the nonvolatile memory is rewritten, the loader program of the CPU 12 is executed at high speed.