In the following cases, the remaining 10 bits identify a particular I/O device or memory location. Show the program executions (contents of IR, PC, AC) for the following program where the following instructions are executed from memory locations 300, 301, 302 respectively.
A. Load Register 1 from Device 5. Assume that the next value retrieved from device 5 is 30.
B. Add content of Register 2. (Assume that register 2 contains a value of 20.)
C. Store AC to device 6
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[10 Points]
3456
15
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Opcode
Address
a Instruction format
Magnitude
(b) Integer format
Program Counter (PC) = Address of instruction
Instruction Register (IR) = Instruction being executed
Accumulator (AC) = Temporary storage
c Internal CPU registers
The partial list of opcodes (bits 0-3) for the machine are as follows:
0001 = Load AC from Memory
0010 = Store AC to Memory
0011 = Add to AC from Memory
0100 = Load AC from I/O
0101 = Store AC to I/O
0110 = Load Register from Memory
0111 = Store Register to Memory
1000 = Add to AC from Register
The list of registers (bits 4-5) for the machine are as follows:
00 = Register 1
01 = Register 2
10 = Register 3
11 = Register 4