JPS6488628A - Exception processor - Google Patents

Abstract

PURPOSE:To simplify a microprogram necessary for a pre-processing by executing hardware-wise the detection and processing (determination of calculation result) of an exception item in a pre-processing by a numerical arithmetic processor by means of an exception decoder. CONSTITUTION:At the time of pre-processing for arithmetic operation of the numerical arithmetic processor, tags 12, 13 representing the attributes of arithmetic data are inputted to the exception decoder 11 which determines a decoding pattern depending on the kind of the arithmetic operation. The decoder 11, in case the arithmetic processing is unnecessary, outputs an arithmetic processing unnecessary flag, and at the same time outputs selection signals corresponding to the inputted tags 12, 13 and an instruction register 14. In an output means, various constants to be used in an arithmetic output, as well as data to be operated, are stored. The output means, in case of an arithmetic processing is unnecessary is represented by the arithmetic processing unnecessary flag, selects one of the stored arithmetic outputs by the instruction of the selection signal, and outputs it. As a result, the microprogram of a pre-processing in which an exception item is processed can be simplified.