# 1434

1. A hypothetical Machine has the following characteristics:

0 3 4 15

1. Instruction Format 0 1 15 Sign Magnitude
2. Integer Format
Program Counter (PC) = Address of Next Instruction, 12-bits Instruction Register (IR) = Instruction being Executed, 16-bits Accumulator (AC) = Temporary Storage, 16-bits Memory Address Register (MAR) = Address of the memory location being accessed next, 12-bit Memory Buffer Register (MBR) = The Data/Instruction brought/being sent to Memory, 16-bits
3. Internal CPU Registers.
(0001)2 = Load AC from memory
(0010)2 = Store AC to memory
(0101)2 = Add to AC form memory
4. Partial list of opcodes
CPU Registers Memory PC AC IR 300 – – 1940 5941 2941 300 301 302 0003 0002 940 941
5. Initial Position of the Program. All the given values are in hexadecimal format.
6. Show in steps the execution of the above program on the hypothetical machine.
1. What is an Instruction cycle? Give the flowchart for the instruction cycle which shows how the control determines the three possible instruction types.
2. Explain in detail an Interrupt driven I/O operation.
1. What do you understand by DMA transfer and data? Why does DMA have priority over CPU when both request a memory transfer?
2. What are addressing modes of instructions? Explain the various possible addressing modes.
1. Compare zero-, one-, two- and three- address machines by writing programs for each of these four machines to compute the expression:
X = (A + B * C)/(D – E * F)
The instructions available for use for these machines are as follows:

0-Address 1-Address 2-Address 3-Address PUSH M LOAD M MOVE X, Y; X MOVE X, Y; X POP M STORE M ADD X, Y; X ADD X, Y, Z; X ADD ADD M SUB X, Y; X SUB X, Y, Z; X SUB SUB M MUL X, Y; X MUL X, Y, Z; X MUL MUL M DIV X, Y; X DIV X, Y, Z; X DIV DIV M – –