Past exam of the year 1 of the computer science course of the University of Oxford / 2018 / Digital systems, linear algebra, introduction to formal proof / 3 / b

Fetch and decode the MIPS I-type instruction, read $rs$ and $rt$, and subtract their values in the arithmetic logic unit. The zero flag is one exactly when they are equal. The branch target isThe branch selector chooses that target when $B{r}_1=1$ and $B{r}_0=0$ make the diagram's condition equal to $\mathrm{Zero}$. Otherwise it chooses $pc+4$. Neither registers nor data memory are written. The control signals areDashes are don't-care conditions because register write enable is zero. The immediate goes to the branch-target adder, while the main ALU's second input remains the value in $rt$.