Datapath: branch

1. Fetch instruction and increment PC

Fig. 5.21

2. Read 2 registers from register file for comparison

3. ALU subtracts data values, using ALU control to select operation and ALUSrc = 0

4. Generate branch address: add (PC + 4) to sign-extended offset, shifted left by 2

why shifted by 2?  what control signal values?

5. Use Zero output from ALU (and Branch control) to determine which result to use to update PC

If equal, use branch address

else use incremented PC

Note that this is all happening simultaneously in 1 clock cycle (adder separate from ALU)