Question

Instruction set architecture R: register X, Y, Op1, Op2: Operand Quantity: constant value EA: Effective memory address Opcode Operation Name MOV X Y XCH Opl, Op2 ADD X, Y SUB X, Y SAL Op. Quantity SAR Op. Quantity SHR Op Quantity AND X, Y OR X. Y XOR X, Y NOT X LOAD RA LOAD R. (A) STORERA STORE R. (A) Description Move data from Y to X Exchange Opl with Op2 X=X+Y X=Y-X Shift Arithmetic Left on Op for Quantity Shift Arithmetic Right on Op for Quantity Shift Right on Op for Quantity Perform bitwise AND operation and put the result in X Perform bitwise OR operation and put the result in X Perform bitwise XOR operation and put the result in X Perform bitwise NOT operation and put the result in X EA- A Direct memory address EA = (A) W Indirect memory address EA = A Direct memory address EA=(R) Indirect memory address 1. In order to implement the above instruction set, how many bits do we need for the opcode? 2. What are the contents of register R after executing the following two instructions: (all numbers are hexadecimals.) MOV R, FO // Moves data (FO) into register R AND R, 78 //Logical operation (and) with data 78 3. What are the contents of register R after executing the following two instructions: (all numbers are hexadecimals.) MOV R, AA // Moves data (AA) into register R XOR R, FF //Logical operation (XOR) with data FF 4. What are the contents of register R after executing the following two instructions: (all numbers are hexadecimals.) MOV R, AB // Moves data (AB) into register R OR R,00 //Logical operation (or) with 00

Answer 1

1. Total number of instructions given in the instruction set is: 15

Number of bits for opcode = log₂ (15) = 4

Therefore, we need 4 bits for opcode.

2. The answer is: 70 (hexadecimal)

• Perform AND operation between F0 (1111 0000) and 78 (0111 1000)

3. The answer is: 55 (hexadecimal)

• Perform XOR operation between AA (1010 1010) and FF (1111 1111)

4. The answer is: AB (hexadecimal)

• Perform OR operation between ​​​​​​​AB (1010 1011) and 00 (0000 0000)