1. In a microprogrammed data processor wherein a sequence of microwords are used to control the execution of each processor instruction, an improved microword control mechanism comprising: circuitry responsive to the processor instruction to be executed for providing an instruction dependent signal uniquely representative of such instruction; sequence counter circuitry for supplying a sequence of number signals; and a programmable logic array responsive to the instruction dependent signal and to the sequence of number signals for producing a sequence of microwords needed to execute the instruction.