from the control unit. Thus, reading a microinstruction from the control memory is
the same as executing that microinstruction.The third element shown in the figure is
a sequencing unit that loads the control address register and issues a read command.
Let us examine this structure in greater detail, as depicted in Figure 16.4.Comparing
this with Figure 16.4,we see that the control unit still has the same inputs (IR,ALU
flags, clock) and outputs (control signals).The control unit functions as follows: