So, the 10bit +1 adder is finished...it will be used to increase the program-counter, the most common case. The reason why the system will not use the ALU for  the +1 loop (inluding a temp-register) for the program-counter is...to be faster with the common case.

During the week the adder will be tested and the timings will be analyzed using a oscilloscop. It is an important question...how fast is the adder in the worst case.