Question :

Suppose a "SUMOF2" instruction needs to be added to the small computer. The main job if this instruction is to take the sum of the data in two consecutive memory locations and store the result in [M+1] i.e ([M+1] = [M]+[M+1]), assume that ALU has an adder unit to take that can take the summation of two numbers when the controller issue the signals ALU code: 111. if the ALU code: 000 means bypass any number to AC directly, notice that AC has to be unchanged.

a. Will the format of the instruction and control signals change in this case or not ? why?

b. Using the controller state diagram constructed in class to show the fetch and execute cycles for this instruction. (Hint: fetching the instruction are common cycles.

c. Show any modification that is needed to the data path to support the execution of this instruction if any.

d. If the job of this instruction is changed a little to take the average of two consecutive memory locations and store the result in AC (AVGOF2), show any possible changes in the fetch, execute cycles or data path of this instruction if any?

(hint: shift right to do a average of two) CDA

e. If the job of this instruction is changed a little to take the average of 8 consecutive memory locations and store the result in memory (AVGOF8), show any possible changes in the fetch, execute cycles or data path of this instruction if any?

( hint: use 3-bit counter in your data path to count a chive 8-time counting with an input signal count to the controller)