Patent ID: 6925548

Claim:
A data processor for processing an instruction that includes a first operation code field, a second operation code field, and an execution sequence specifying field for specifying an execution sequence of a plurality of operations specified by a plurality of operation code fields including the first operation code field and the second operation code field, said data processor comprising: instruction decoding means for decoding instructions; and instruction executing means for executing the instructions according to a decoded result by said instruction decoding means, wherein said instruction decoding means includes: first decoding means for decoding the first operation code field when an operation specified by the first operation code field is executed in a first execution sequence in accordance with a content specified by the execution sequence specifying field; second decoding means for decoding the second operation code field when an operation specified by the second operation code field is executed in the first execution sequence in accordance with the content specified by the execution sequence specifying field; and decision means for making a decision as to which one of decoding means including said first decoding means and said second decoding means is to be used for decoding the operation code field to be executed in a second or subsequent execution sequence in accordance with the content specified by the execution sequence specifying field, and wherein said instruction executing means comprises: means for executing a first operation in response to the decoded result by said first decoding means when the first operation code field has a first bit pattern, and when the operation specified by the first operation code field is executed in the first execution sequence according to the execution sequence specifying field; and means for executing a second operation different from the first operation in response to the decoded result by said second decoding means when the second operation code field has the first bit pattern, and when the operation specified by the second operation code field is executed in the first execution sequence according to the execution sequence specifying field.