In the case of a hard-wired control unit the control matrix is responsible for sending out the required sequence of signals. Each bit of a microinstruction might correspond to one control signal. If the bit is set it means that the control signal will be active; if cleared the signal will be inactive. Sequences of microinstructions could be stored in an internal "control" memory. Execution of a machine language instruction could then be caused by fetching the proper sequence of microinstructions from the control memory and sending them out to the data path section of the computer. A sequence of microinstructions that implements an instruction on the external computer is known as a micro-routine. The heart of the controller is the control 32 X 24 ROM memory in which upt to 32 24-bit long microinstructions can be stored. Addresses provided to the control ROM come from a micro-counter register The micro-counter, in turn, receiv...
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