Abstract: A variable frequency dividing circuit according to this invention switches a frequency division ratio immediately after a neew frequency division ratio has been input, and then performs a frequency dividing operation without discarding already counted values. This frequency dividing circuit generates an error signal if a newly input frequency division ratio differs from the previous frequency division ratio and the already counted value is larger than the new frequency division ratio. Furthermore, the frequency dividing circuit performs forcibly a frequency division completion processing according to the consecutively input frequency signal.

Abstract: A method of controlling a plurality of electrical devices which control an operation of an internal combustion engine wherein an operation period of time required for each of the electrical devices is computed by computing means in response to operating conditions of the engine, the computed required operation period of time is counted by time-counting means, and each of the electrical devices is caused to operate during the counting. At each start of the time-counting from the computing means, a different one of the electrical devices is selected and the operation thereof is started, an interrupt signal is generated when the time-counting means has counted up, and the operation of the selected different one of the electrical devices is deenergized in response to the generation of the interrupt signal. Preferably, the time-counting means comprises a signal time counter.

Abstract: Fuel injection is started through a first one of fuel injection valves, and a time counter counts a period of time elapsed from the start of fuel injection through the first one valve. Fuel injection is started through a second one of the fuel injection valves when a predetermined period of time elapses after the start of fuel injection through the first one valve. The fuel injection through the first one valve is terminated in response to completion of counting of the time counter, and the time counter is restarted to count a difference between a desired fuel injection period of time for the first one valve and a desired fuel injection period of time for the second one valve. The fuel injection through the second one valve is terminated in response to completion of counting of the restarted time counter.

Abstract: An engine control system includes a pulse generator for generating a synchronous pulse signal synchronously with the speed of rotation of an engine, a timer for generating a timer pulse signal of a constant period, and a microcomputer having an interrupt input terminal for receiving the pulse signals as interrupt signals and operable to start processing operations in response to the interrupt signals, so that a number of controlled objects of the engine can be controlled on the basis of data indicative of operating conditions of the engine. Data is processed in response to an interrupt caused by the synchronous pulse signal to control a first-group controlled object of the number of controlled objects and setting a flag to request processing of data items related to the first-group controlled object.

Abstract: A microcomputer includes an interrupt signal generator for supplying a CPU with an interrupt signal at predetermined time intervals, and a monitoring timer reset by a reset signal generated by the CPU in response to the interrupt signal. An abnormality is sensed on the basis of expiration of time in the monitoring timer. A flag for resetting the monitoring timer during a first processing started by the interrupt signal is stored in a memory device connected to the CPU, and the CPU generates the reset signal in response to the stored flag during a second processing having a priority lower than that of the first processing.

Abstract: The present invention relates to a method of detecting the number of revolutions of an internal combustion engine. Utilizing the presence of a certain multiple relationship between the period of a top dead-center signal and the period of a cylinder discrimination signal, the present invention is constructed so that, with respect to clock signals to be counted for detecting the number of revolutions, between the period of a clock signal used when using the top dead-center signal and the period of a clock signal used when using the cylinder discrimination signal there exists a multiple relationship which is the same as the multiple relationship between the period of the top dead-center signal and that of the cylinder discrimination signal.

Abstract: A fuel supply control control method for an internal combustion engine, which is adapted to determine a quantity of fuel for supply to the engine by multiplying a basic value of the quantity of fuel determined as a function of at least one operating parameter of the engine, by correction coefficients dependent upon operating conditions of the engine, and adding to the basic value correction variables dependent upon operating conditions of the engine, and to supply the determined quantity of fuel to the engine. Values of predetermined one of the above correction coefficients and predetermined one of the above correction variables are determined, which correspond to a set desired value of output voltage of a single voltage creating means. The basic value of the quantity of fuel is corrected by the determined values of the predetermined one correction coefficient and the predetermined one correction variable through multiplication and addition, respectively, to determine the quantity of fuel.