Abstract: A first selector outputs either an output of an ALU (arithmetic logic unit) or a first clipped value to a first bus. A temporary register holds the output signal of the ALU, and a second selector outputs either the output signal of the temporary register or a second clipped value. A controller causes an operation result regarding lower data of first and second operands to be stored in the temporary register in a first cycle of the ALU when each of the first and second operands consists of 2n bits while the ALU operates on n bits per cycle thereof. When an operation result regarding upper data of the first and second operands overflows in a second cycle of the ALU, the controller causes the first and second selectors to output the first and second clipped values. When the operation result regarding the upper data does not overflow, the controller causes the first and second selector to respectively output the output signals of the ALU and the temporary register.

Abstract: In a closed loop idle engine speed control system the actual engine speed is compared with a reference idle speed during engine warm-up periods to control the amount of an air flow introduced to the engine through an auxiliary air delivery system so that the difference between the actual and reference engine speeds is reduced. The reference setting of the idle speed is varied as a function of the engine temperature in order to vary the actual engine speed in response to an increase in the engine temperature. The auxiliary air delivery system includes a linear solenoid type electromagnetic valve which comprises a spring-biased valve member normally maintained in a neutral position with respect to the valve seat to allow introduction of a predetermined amount of auxiliary air to the engine and a pair of coils energized respectively with a current representing the difference in engine speed to move the valve member in opposite directions to increase or decrease the auxiliary air supply.