Hitachi, Ltd.

Hitachi Vlsi Engineering Corp.

Hitachi Microcomputer System, Ltd.

Other

Renesas Technology Corp.

Toshimasa Kihara

Yasushi Akao

Mitsuru Watabe

Shiro Baba

Kouki Noguchi

Keiichi Kurakazu

Takanaga Yamazaki

Shumpei Kawasaki

Takashi Tsukamoto

Shigeki Masumura

Yugo Kashiwagi

Masahiro Kainaga

Kaoru Fukada

Eiji Sakakibara

Yoichi Asano

Katsuhiko Ishida

Yasuhiro Tawara

Shuya Fujita

Noriko Sawa

Hideaki Chaki

Tadahiko Sugawara

Hideaki Takahashi

Minoru Fukuda

June Sugiura

Fumio Tsuchiya

Kiyoshi Matsubara

Naoki Mitsuishi

Tadashi Yamaura

Koyo Katsura

Satoshi Meguro

Hideo Maejima

Kazuhiro Komori

Hideo Nakamura

Yoshimune Hagiwara

Satoru Ito

Terumi Sawase

Toshiro Tsukada

Harumi Wakimoto

Norishige Kawashimo

Toshifumi Inoue

Herein disclosed is a microcomputer MCU adopting the general purpose register method. The microcomputer is enabled to have a small program capacity or a high program memory using efficiency and a low system cost, while enjoying the advantage of simplification of the instruction decoding as in the RISC machine having a fixed length instruction format of the prior art, by adopting a fixed length instruction format having a power of 2 but a smaller bit number than that of the maximum data word length fed to instruction execution means. And, the control of the coded division is executed by noting the code bits.

Microcomputer and dividing circuit

A microcomputer MCU adopting the general purpose register method is enabled to have a small program capacity or a high program memory using efficiency and a low system cost, while enjoying the advantage of simplification of the instruction decoding as in the RISC machine having a fixed length instruction format of the prior art, by adopting a fixed length instruction format having a power of 2 but a smaller bit number than that of the maximum data word length fed for instruction execution. And, the control of the coded division is executed by noting the code bits.

Central processing unit having instruction queue of 32-bit length fetching two instructions of 16-bit fixed length in one instruction fetch operation

A microcomputer CMU adopting the general purpose register method is enabled to have a small program capacity or a high program memory using efficiency and a low system cost, while enjoying the advantage of simplification of the instruction decoding as in the RISC machine having a fixed length instruction format of the prior art, by adopting a fixed length instruction format having a power of 2 but a smaller bit number than that of the maximum data word length fed for instruction execution. And, the control of the coded division is executed by noting the code bits.

Microcomputer having variable bit width area for displacement and circuit for handling immediate data larger than instruction word

A branch instruction format has different respective field lengths for conditional branch instructions and unconditional branch instructions. A conditional branch instruction has a first bit length and a first area for a displacement designating an address to be jumped, wherein the first area has a second bit length that is smaller than the first bit length. An unconditional branch instruction also has the first bit length, and a second area for a displacement designating an address to be jumped, wherein the second area has a third bit length that is different from the first and second bit lengths.

Branch instruction having different field lengths for unconditional and conditional displacements

Microcomputer having variable bit width area for displacement

Central processing unit having instruction queue of 32-bit length

Microcomputer having variable bit width area for displacement and

A division method and circuit performs a division for signed data by adding or subtracting a divisor to or from the dividend or the partial remainder from the division, according to the sign of the divisor or the dividend and the partial remainder to acquire a new partial remainder. The division is repeated a predetermined number of times in which a quotient bit is acquired according to the sign of the acquired partial remainder or the divisor. The dividend is corrected by subtracting 1, which is the significance of an LSB of the corresponding dividend, from the dividend when the sign of the dividend is negative, and the corrected dividend is used for the division processing.

Division circuit and the division method thereof

Microcomputer having 16 bit fixed length instruction format

A single chip type microcomputer includes at least a central processing unit (CPU), a random-access memory (RAM), a mask read-only memory (mask ROM) and an electrically writable ROM such as an electrically erasable and programamble read-only memory (EEP-ROM). The electrically writable ROM stores both the user program and data to be preserved. The microcomputer includes further memory for storing a write control program for controlling the write operation to the writable ROM, and the electrically writable ROM and the memory are disposed to mutually different address positions on the address space of CPU. The proportion of size of the user program region and the data region in the writable ROM can be selected in a free proportion. A timer governs writes to the writable ROM.

System for performing writes to non-volatile memory elements in a

A single chip type microcomputer includes at least a central processing unit (CPU), a random-access memory (RAM), a mask read-only memory (mask ROM) and an electrically writable ROM such as an electrically erasable and programmable read-only memory (EEP-ROM). The electrically writable ROM stores both the user program and data to be preserved. The microcomputer includes further memory for storing a write control program for controlling the write operation to the writable ROM, and the electrically writable ROM and the memory are disposed to mutually different address positions on the address space of CPU. The proportion of size of the user program region and the data region in the writable ROM can be selected in a free proportion. A timer governs writes to the writable ROM.

Easy testability and data security of an electrically erasable programmable read only memory (EEPROM) can be accomplished by disposing pads and an input/output (I/O) circuit providing addresses, data and control signals necessary for the EEPROM test on a semiconductor substrate and by disposing a two-level test I/O interception circuit consisting of an EEPROM device on the substrate such that once the testing is completed, unauthorized accessing is prevented from outside the semiconductor substrate as a result of having a built-in data security function. A microcomputer having this capability is provided with a central processing unit (CPU) for processing data, a memory, such as an EEPROM, which is internally communicating through a common bus (which transmits data, address and control signals) with the CPU, other than during a test mode, and first and second inhibition circuits which provide the security. The first inhibition circuit is coupled to the data bus and provides a first inhibition operation to prevent access operations to the memory. The first inhibition circuit release the first inhibiting operation in accordance with a signal from outside the semiconductor substrate or body. The second inhibition means is coupled to the data bus and provides a second inhibiting operation to prevent access operations to the memory from outside the semiconductor body via the data bus and permanently disables the access operations to the memory irrespective of a releasing or termination of the first inhibiting operation after the second inhibiting operation has taken effect.

Microcomputer having a PROM including data security and test circuitry

An electrically programmable read only memory is equipped with latch circuits for sequentially introducing series signals which are fed through external terminals. The converter includes sequentially operated switch elements and latch circuits in order to convert the series signals into parallel signals. The thus converter parallel signals are written simultaneously in a memory array via address decoder operated selection switch elements. According to this method, the writing operations into the memory array can be conducted at a high speed even when one writing operation is relatively long as a result of the parallel signal action.

Semiconductor memory

An electrically programmable read only memory is equipped with latch circuits for sequentially introducing series signals which are fed through external terminals. The converter includes sequentially operated switch elements and latch circuits in order to convert the series signals into parallel signals. The thus converted parallel signals are written simultaneously in a memory array via address decoder operated selection switch elements. According to this method, the writing operations into the memory array can be conducted at a high speed even when one writing operation is relatively long as a result of the parallel signal action.

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Tachikawa, Japan

Toshimasa Kihara