Rohm Co., Ltd.

Hiroaki Masumoto

Shigemi Chimura

Yoshiaki Suenaga

An option setting circuit includes a set circuit with respect to which an option is set, a non-volatile memory for storing an option data for setting the set circuit which memory is provided exclusively for the set circuit, and a latch circuit which latches an option data provided from the non-volatile memory and provides the data to the set circuit.

Option setting circuit and an integrated circuit apparatus including the

In a microcomputer, a circuit is provided which performs the option setting of the condition of an I/O port. The option setting is repeatedly performed while the microcomputer is operating. As a result, even if the option setting is changed to an incorrect setting due to noise from external sources, the incorrect option setting is immediately returned to the correct setting. Moreover, the option setting is never reset at the time of resetting other than the resetting performed at the time of the turning on of the power.

Option setting circuit for interface circuit

A one-chip microcomputer according to the present invention is provided with an initial reset circuit for producing a first initial reset signal having a first reset period and a second initial reset signal having a second reset period which is longer than the first reset period, an access circuit for gaining access to an address in a nonvolatile memory such as a built-in ROM to read data therefrom, and I/O buffer circuits. A storage circuit and an I/O buffer connected to a programmable I/O terminal are provided in the I/O buffer circuit and a function of the I/O terminal with options is selected in conformity with the data set in the storage circuit. The data stored at a predetermined address in the nonvolatile memory is transferred to the storage circuit by operating the access circuit until the termination of the reset period of the second initial reset signal after the termination of the first reset period of the first initial reset signal. With this arrangement, as the contents of write data are altered by writing the data to the nonvolatile memory from the outside, an optional function of the programmable I/O terminal can be selected in accordance with the alteration.

One chip microcomputer having programmable I/O terminals programmed

The improved CMOS output circuit has an enhancement-type PMOS and an enhancement-type NMOS connected in order between a power supply line and a reference potential line and that has the junction between the PMOS and the NMOS connected to an output terminal. The PMOS is such that a P-type region is provided in the back gate region to form a diode, with the back gate region being connected to the power supply line via the diode. A switch circuit is inserted between the gate of this PMOS and said junction or the output terminal. When a voltage higher than the voltage on the power supply line is applied to the output terminal, the applied voltage will turn on the switch circuit.

Growing community of inventors

Kyoto, Japan

Hiroaki Masumoto