| 摘要 |
Improved means and methods for providing highly flexible microinstruction sequencing in a microprogrammed digital data processing system particularly with regard to the handling of specialized types of sequencing situations such as are involved in wait-loop and repeat situations. The microprogramming control system is implemented using a plurality of programmable read only memories storing control words chosen so as to provide for microinstruction sequencing in a manner which in the first instance assumes that no branching possibilities are present, even though one or more branching possibilities may in fact be present in the microinstruction flow path, thereby permitting very fast microinstruction sequencing when the assumed sequencing is correct. Means are provided for monitoring the correctness of microinstruction sequencing concurrently with the execution of a microinstruction during each cycle for which a branching decision is required, and for correcting an incorrect assumed sequence in a highly flexible manner with minimum penalty on processing time using microinstruction indexing and inhibiting signals which are selectively provided in response to the states of selected system conditions during the cycle. Means and methods are also provided to permit the implementation provided for monitoring and correction to also be used to provide greater flexibility in the handling of specialized types of sequencing situations such as are involved in wait-loop and repeat situations.
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