| 摘要 |
PURPOSE:To correct error with a microprogram even in the case of error in an instruction decoding circuit by indicating the address, which is generated from an instruction code and an exception code in software, to a wrong exception code detection memory and storing a correct exception code as contents of the address. CONSTITUTION:An instruction fetch register 1 which reads out an instruction in software from a storage circuit and holds this instruction, and an instruction decoding circuit 2 which decodes the instruction in the instruction fetch register 1 and generates the exception code indicating which specifications the instruction violates in the case of the violation of specifications are provided. A wrong exception code detection memory 3 is provided which takes the instruction held in the instruction fetch register 1 and the exception code as the address to output stored contents. Thus, the microprogram of exception handling is easily corrected even n the case of error (bug) in hardware. |
