| 摘要 |
A data processor decoding and executing a train of instructions of variable length. The data processor includes a first instruction control means for temporarily storing a prefetched instruction code and sequentially outputting said instruction code with units of a predetermined number of bits, and a second instruction control means for decoding an instruction code fed from the first instruction control means, generating control information for data processing based on the decoding, and outputting data indicating instruction update demand quantity to the first instruction control means. Based on the data indicating the update demand quantity, the first instruction control means judges whether it has output a valid instruction code of length exceeding the update demand quantity, and provides an indication of validity or invalidity of the decoded instruction code and controls updating of the instruction code based on a result of the judgement. As a result, it becomes possible to reduce time necessary for the supply of instruction codes and thus improve a data processing speed as the entire processor.
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