Microprogram control

Claim 1

Data processing apparatus comprising: (a) an instruction register for holding a machine-level instruction, (b) a plurality of separate functional units for performing data processing operations, (c) a plurality of microprogram stores, one for each of said functional units, each store holding a plurality of sequences of microinstructions, (d) a plurality of decoders connected respectively to said microprogram stores, for decoding said microinstructions to produce control signals for the respective functional units, (e) phase control means, responsive to the machine-level instruction in said instruction register, for producing a succession of phase signals indicating a succession of phases required to execute that machine-level instruction, (f) microprogram sequencing means responsive to each said phase signal to initiate one of said sequences of microinstructions in each said microprogram store, (g) parameter generating means for generating a plurality of microprogram parameters, from the machine-level instruction in said instruction register, (h) parameter selection means, controlled by said phase signals, for selecting a predetermined sub-set of said parameters during each said phase, and (i) a multi-line bus for applying the selected parameters in parallel to all said decoders to qualify operation of said decoders.