Abstract: An information processor has at least one interface unit by which the processor is coupled to a peripheral equipment. The interface unit can selectively generate either a first mode signal or a second mode signal when the processor performs and interruption operation according to request from the peripheral equipment. When the processor performs the interruption operation in response to the first mode signal, a stack operation for saving information necessary to restart a program execution which is stopped by the interruption to a stack memory is performed before start of the interruption operation. While the processor can perform the interruption operation in response to the second mode signal without the stack operation, whereby an improved processor with less overhead can be provided.

Abstract: An information processor has at least one interface unit by which the processor is coupled to a peripheral equipment. The interface unit can selectively generate either a first mode signal or a second mode signal when the processor performs an interruption operation according to request from the peripheral equipment. When the processor performs the interruption operation in response to the first mode signal, a stack operation for saving information necessary to restart a program execution which is stopped by the interruption to a stack memory is performed before start of the interruption operation. While the processor can perform the interruption operation in response to the second mode signal without the stack operation, whereby an improved processor with less overhead can be provided.

Abstract: An apparatus for processing a plurality of tasks comprises a central processing unit (CPU) equipped with a microprogram memory, and a memory. A processing demand to the real time OS required for the execution of the multitask processing is treated as exclusive instruction. For this purpose, the system includes a decoder for decoding the exclusive instruction, and the CPU or the memory has a microprogram for the realization of the instruction.

Abstract: An information processor has at least one interface unit by which the processor is coupled to peripheral equipment. The interface unit can selectively generate either a first mode signal or a second mode signal when the processor performs an interruption operation according to request from the peripheral equipment. When the processor performs the interruption operation in response to the first mode signal, a stack operation for saving information necessary to restart execution of a program which is stopped by the interruption in a stack memory is performed before the start of the interruption operation. The processor can perform the interruption operation in response to the second mode signal without the stack operation, providing an improved processor with less overhead. The two interruption mode technique is described in a number of applications, including D/A conversion, serial data transmission and reception, and operation of computer peripheral devices.