| 摘要 |
PURPOSE:To prevent an arithmetic exception detecting mechanism from affecting the performance of the floating point arithmetic by checking a fact that the valid digit information is not included in a digit range of the interim result instructed from an exponent decoding means and that the mantissa of the interim result is not equal to zero. CONSTITUTION:A valid digit detector 9 detects whether the mantissa output 58 of the interim result of a multiplier 3 is equal to zero or not every 4 bits of each digit and outputs the result of this check. An exponent part decoder 10 outputs the information 59 which designates the test conditions of the output 60 received from the detector 9 for detection of an arithmetic exception out of an exponent 57 of the interim result. An exception detector 11 detects an arithmetic exception 62 based on the information received from a valid digit detector 8 and the decoder 10. In other words, the detector 11 detects an exponent underflow exception 62 based on the valid digit information 60 on a mantissa of the interim result produced by the detector 9 and the exception detecting conditions 59 produced by the decoder 10. Thus it is possible to prevent an arithmetic exception detecting mechanism from affecting the performance of the floating point arithmetic. |
