| 摘要 |
PURPOSE:To omit the undefined instruction decoding area and to add easily the insturcting function, by using a specific address where all address selecting lines are outputted at non-selection as the initial address of an undefined instruction processing microroutine. CONSTITUTION:An instruction decoder 11 and an initial address generator 12 store only the information relating to a defined instruction. An instruction word read out from a main storage is decoded at the instruction decoder 11, and the initial address of the microprogram corresponding to the instruction word from the initial address generator 12 receiving the output is generated. When the instruction words read out from the main storage is an undefined instruction, 0 is all given to an address selecting line 1a. As a result, an address 0 is outputted from the initial address generator 12 and branched to an undefined instruction processing routine started from the address 0. |
