Sharp Kabushiki Kaisha Corporation

Nippon Telegraph and Telephone Corporation

Other

Kazuhiro Yaegawa

Tadao Takeda

Masaaki Tanno

Hiroki Suto

Ryuichi Ogawa

Masaki Wakabayashi

Masahiro Yoshizawa

Nobuhiro Shimoyama

Haruhiko Shigemasa

Susumu Kurioka

Kenji Ohno

Hiroki Sutou

Masafumi Katsutani

A 1-chip microcomputer of the present invention has (a) a monitor flag for setting a flag indicating that a specified address space is accessed, (b) an access permission address range setting register, for setting an address range in which an access is permitted while the flag is set, (c) an access permission area detection circuit for judging whether the access is made within the address range thus set, (d) an access permission setting register, for setting whether or not an access with respect to an address other than the address range should be permitted, and (e) memory read-out control circuit and memory writing control circuit for controlling an access with respect to a nonvolatile memory based on a result thus judged and content set by the access permission setting register. With the arrangement, it is possible to provide a 1-chip microcomputer that maintains the security among application programs.

1-chip microcomputer having controlled access to a memory and IC card using the 1-chip microcomputer

When a built-in nonvolatile memory in a microcomputer is tested, a control program prestored in a boot ROM is run upon entering a test command from an external communication device; a test program is transferred from the external communication device to a built-in RAM through a communication circuit; a control of a CPU is switched to the built-in RAM after the test program has been transferred and a test is conducted on the nonvolatile memory; and a test result and a fail log are transferred to the external communication device through the communication circuit. Consequently, the built-in nonvolatile memory in the microcomputer can be checked without leaving the test program on the chip.

Microcomputer having built-in nonvolatile memory and check system thereof and IC card packing microcomputer having built-in nonvolatile memory and check system thereof

In order to provide a built-in self testing function, a one-chip microcomputer is equipped with an activation register for activating the test operation and a built-in self test activation pattern generator for setting initial values at test control circuits (pseudo random number generator, logical circuit testing compressor, pattern generator, and memory testing compressor). In accordance with an instruction from the CPU, a built-in self test is activated so that the results of tests of the memory and the group of logical circuits are read from the memory testing compressor and the logical circuit testing compressor, and respectively compared with expected values preliminarily stored in the memory in the one-chip microcomputer; thus, the results are diagnosed. Thus, it is possible to carry out a built-in self test without using a plurality of exclusively-used test terminals.

One-chip microcomputer and control method thereof as well as an IC card having such a one-chip microcomputer

A 1-chip microcomputer having a built-in nonvolatile memory includes at least one erasable flash memory provided in a memory space of the microcomputer, a boot ROM for storing an initial program to start up the 1-chip microcomputer and a transfer program to transfer the initial program to the flash memory, and control means for, when the flash memory stores no program, transferring the initial program to the flash memory in accordance with the transfer program and subsequently removing the boot ROM from the memory space. Consequently, even if a new program is additionally stored to the nonvolatile memory in the 1-chip microcomputer, the additional program can be carried out.

Microcomputer having built-in nonvolatile memory for simultaneous use as a program area and a data area

When an IC card is attached to a terminal unit, a counter counts pulses of an external clock signal and a switching circuit outputs the external clock signal to an internal circuit in place of an internal clock signal if a NAND gate determines that the count of pulses of the external clock signal by the counter is a predetermined value. When the IC card is ejected from the terminal unit, pulses of the internal clock signal are counted by a counter and when the count attains a predetermined value, the counter is cleared and the switching circuit outputs the internal clock signal to the internal circuit in place of the external clock signal in response to the output of the NAND gate. Thus, it can be correctly determined whether the IC card is operated in the form of a single body or in the form attached to any terminal unit.

Clock signal switching device of an IC Card

Growing community of inventors

Yamatokoriyama, Japan

Kazuhiro Yaegawa