Abstract: A memory management apparatus uses a link list memory to manage a use area and a vacant area of a data memory. The use of the use area of the data memory by each of plural ports is restricted, and the use area of the data memory is configured to be always provided for each of the plural ports. In this manner, monopolized use of the data memory by a specific port is prevented and each of the plural ports is securely provided with the use area of the data memory under control of the memory management apparatus.

Abstract: During software development, a multichip module is used which encloses a target chip and a development chip in one package. A CPU of the development chip fetches instructions from a flash memory in the chip to execute them, and accesses RAM and peripheral circuits in the chip. For motor control circuits that exist only in the target chip, the CPU accesses them via serial communication. When the one-chip microcomputer operates alone, its CPU switches a switching circuit to a JTAG interface side to actuate a motor control circuit via internal serial communication.

Abstract: A microcomputer and method are provided capable of restarting a rewrite program without the need for changing a mode using an external terminal when rewriting nonvolatile memory fails. A CPU of a microcomputer executes a rewrite program to clear FLASH status 0 of flash memory and rewrite all areas in it. The CPU finally writes a rewrite completion code to FLASH status 0. The CPU executes a determination program to read FLASH status 0 of the flash memory. The CPU reads ID status information when read data does not match the rewrite completion code. The CPU re-executes the rewrite program when the data matches ID status information.

Abstract: A RISC type of CPU is provided to execute an object program in which a stack area is used. The CPU is configured to have a return instruction based on an operand at which an open size is specified and to perform the return instruction when the stack area is required to be opened in returning processing executed by the CPU from interrupt processing to ordinary processing with no interrupt. Also a compiler is provided to compile a source program into the object program. The compiler determines whether or not a stack area in the source program is required to be opened when processing in the source program is returned from interrupt processing to ordinary processing with no interrupt and produces codes of the object program in which an operand for a return instruction is included and an open size for the stack area is specified at the operand.

Abstract: In a DPLL circuit, when the size of a data value which is output from a data latch circuit and should be naturally set in a 11-bit down-counter becomes equal to or more than 12 bits, an overflow preventing circuit substitutes the 11-bit data for the data value.

Abstract: A single-chip microcomputer includes a logic circuit, a CPU and a flip-flop for synchronizing an interrupt-request signal, which is supplied by the logic circuit to the CPU, based on a clock signal. A multi-chip emulation apparatus comprises a peripheral evaluation chip, a CPU evaluation chip and a device, which are used for emulating functions of the logic circuit, the CPU and the flip-flop respectively. When the multi-chip emulation apparatus is used for emulating functions of the single-chip microcomputer in the development, the device for emulating functions of the flip-flop synchronizes the interrupt-request signal to absorb a delay time incurred by the interrupt-request signal due to a physical distance between the peripheral evaluation chip and the CPU evaluation chip so that an interrupt-handling timing in the emulation matches an interrupt-handling timing in the real operation of the single-chip microcomputer.

Abstract: In an EEPROM of a microcomputer, data is stored for determining a communication rate CMR for fixing the data transmission time of one frame managed by a communication circuit on the basis of an oscillation output characteristic of a CR oscillating circuit that varies in accordance with temperature. CPU reads out data stored in EEPROM in accordance with the temperature detected by a temperature detecting circuit, and sets the determined communication CMR into the communication circuit.

Abstract: A microcomputer includes a main oscillator for generating and outputting a main clock signal, a sub oscillator for generating and outputting a sub clock signal, a central processing unit that operates based on the main clock signal, a signal output circuit that operates based on the sub clock signal and outputs a timing signal at a predetermined interval, and a voltage monitoring circuit that operates based on the sub clock signal and intermittently performs a voltage monitoring function in response to the timing signal. The sub oscillator operates independently of the main oscillator.

Abstract: A microcomputer system includes a CPU, a memory, and a runaway detector. The CPU includes a controller for outputting a task information signal. The task information signal is activated, if the CPU performs the most important task at the present time. A program for the most important task is stored in the memory. The runaway detector includes an address register and a program area checker. The address register stores start and end addresses of the program area. The program area checker determines whether an execution address of the CPU is within the program area by comparing the execution address with each of the start and end addresses. The runaway detector detects a task runaway in the event of conflict between the task information signal and a result of a determination of the program area checker.

Abstract: A reset detection circuit for a logic circuit and a RAM includes a first determining circuit, a second determining circuit and a reset signal generating circuit. The first determining circuit operates with a first voltage and determines whether a second voltage is equal to or higher than a reset voltage for the logic circuit. The second determining circuit operates with the first voltage and determines whether the first voltage is equal to or higher than a minimum operating voltage as a guarantee voltage for an operation of the first determining circuit. The reset signal generating circuit outputs a reset signal for resetting the logic circuit and the RAM, when the first voltage is lower than the minimum operating voltage and the second voltage is lower than the reset voltage.

Abstract: A communication system includes: a master; a plurality of slaves; and a bus for coupling among the master and the plurality of slaves in order to communicate asynchronously among the master and the plurality of slaves. The master supplies electricity to the bus in a power supply period. The master or the slave drives the bus for transmitting a one-bit data through the bus in a data transmission period. The power supply period and the data transmission period are successively performed so that data communication provided by a plurality of one-bit periods is performed among the master and the plurality of slaves. The master finely changes a communication frequency in the data communication. The master changes a drive level of the bus within a predetermined acceptable range in the data communication.

Abstract: A reset detection circuit for a logic circuit and a RAM includes a first determining circuit, a second determining circuit and a reset signal generating circuit. The first determining circuit operates with a first voltage and determines whether a second voltage is equal to or higher than a reset voltage for the logic circuit. The second determining circuit operates with the first voltage and determines whether the first voltage is equal to or higher than a minimum operating voltage as a guarantee voltage for an operation of the first determining circuit. The reset signal generating circuit outputs a reset signal for resetting the logic circuit and the RAM, when the first voltage is lower than the minimum operating voltage and the second voltage is lower than the reset voltage.

Abstract: In a clamp circuit device, reference voltages are set up by a series circuit of an FET, a resistor and an FET. Gate potentials of FETs are set up by performing addition and subtraction of these reference voltages and a reference voltage generated by a bandgap reference circuit, respectively. The clamp circuit device is constructed by connecting together a source of the one FET with its drain connected with the power supply and a source of the other FET with its drain connected with the ground to an input terminal of a control IC unit. Thus, an input voltage is clamped to [V4+Vtp] when an excessive voltage of positive polarity is applied to an input terminal, and the input voltage is clamped to [V5?Vtn] when an excessive voltage of negative polarity is applied.

Abstract: A microcomputer includes an oscillator for generating a clock signal having a frequency by using a CR circuit, a multiplier for outputting the clock signal having a multiplied frequency relative to the frequency generated by the oscillator based on data from an external source, a temperature detection unit for detecting temperature at a proximity of the CR circuit, a storage unit for storing data that enables the multiplied frequency of the clock signal in an output from the multiplier to have a constant value based on a temperature-dependent oscillation characteristic of the oscillator, and a control unit for setting a multiplication value for generating the multiplied frequency of the clock signal to the multiplier based on the data in the storage unit that is correlated to the temperature detected by the temperature detection unit.

Abstract: Integrated circuit device includes: a wiring; a clock signal output circuit including a ring oscillator; an internal circuit; an internal power supply generation circuit for supplying an electric power to the clock signal output circuit and to the internal circuit on the basis of a power supplied from an external circuit; and a capacitor connection terminal. The internal power supply generation circuit supplies the electric power to the ring oscillator through the wiring connecting between the internal power supply generation circuit and the capacitor connection terminal. The internal power supply generation circuit supplies the electric power to the internal circuit through the wiring connecting to the capacitor connection terminal.

Abstract: A semiconductor integrated circuit includes: a package; semiconductor chips in the package including a signal terminal; and a wiring connecting signal terminals. One semiconductor chip is a test object chip including a probe terminal and a test object terminal. The probe terminal connects to an external terminal for testing the test object terminal. The test object chip further includes: a common wiring for connecting the probe terminal and the test object terminal; a first switch for connecting/disconnecting the probe terminal and the common wiring; a second switch for connecting/disconnecting the test object terminal and the common wiring; and a test signal interrupting element for interrupting the test signal to be inputted into an input circuit of the probe terminal.

Abstract: The present invention relates to a clock control circuit apparatus including a first oscillation circuit for generating a first clock signal and a second oscillation circuit for generating a second clock signal and capable of, when the two clock signals are put to use, improving the reliability of oscillation operations thereof. In the clock control circuit apparatus, a sub-clock correction unit corrects an oscillation frequency of a sub-clock signal on the basis of a main clock signal, while a main clock monitoring unit monitors an oscillation state of the main clock signal on the basis of the sub-clock signal.

Abstract: A communication system includes a master control unit, a plurality of slave control units, and buses connecting the master control unit and the slave control units for the asynchronous communication. When the master control unit starts the communication, each slave control unit transmits a plurality of data bits represented by whether the buses be driven to the master control unit in data transmission periods assigned to the slave control units based on a start of communication, and the master control unit drives the buses to insert a period for supplying power while data bits are being transmitted in the data transmission period. The slave control unit provides a non-driving period, which stops driving the buses, at an end of the data bit transmission period.

Abstract: A microcomputer includes a CPU, multiple resources, and an output circuit having an address decoder. The CPU outputs an address signal to the address decoder. The address decoder decodes the address signal and the output circuit outputs a select signal to at least one of the resources in accordance with the decoded address signal. Each of the resources is writable by the CPU when receiving the select signal. When the address signal indicates a predetermined address, the output circuit outputs the select signal to at least two of the resources at a time. Thus, data can be written to the multiple resources at a time. Therefore, the CPU can write the data to the multiple resources within a reduced time by using the output circuit.

Abstract: A microcomputer which is to be utilized in a condition of being built into an apparatus such as a vehicle ECU, includes a ROM having stored therein a program which is prepared by a user and a boot ROM which stores an initialization program for performing at least essential initialization processing which is required for all application programs that will be executed by the microcomputer. The need for the user to generate program contents relating to such initialization processing is thereby eliminated, while increased reliability of operation of the microcomputer is achieved. In addition, it is possible for user-specified initialization data to be read out from a user program and utilized in a part of the initialization processing of the initialization program.