Suppose the hypothetical processor of Figure 1.3 also has two I/O instructions: (15 points)

0011 = Load AC from I/O

0111 = Store AC to I/O

In these cases, the 12-bit address identifies a particular external device. Show the program execution (using format of Figure 1.4) for the following program:

1. Load AC from device 5.

2. Add contents of memory location 940.

3. Store AC to device 6.

Assume that the next value retrieved from device 5 is 3 and that location 940 contains a value of 2.

(a) Instruction format \begin{tabular}{|l|ll|} \hline O & 1 & \\ \hline S & & Magnitude \\ \hline \end{tabular} (b) Integer format Program counter (PC)= Address of instruction Instruction register ( IR )= Instruction being executed Accumulator (AC)= Temporary storage (c) Internal CPU registers 0001= Load AC from memory 0010= Store AC to memory 0101= Add to AC from memory (d) Partial list of opcodes Figure 1.4 Example of Program Execution (contents of memory and registers in hexadecimal)