MICROPROCESSOR AND MICROCONTROLLER

Previous
Next

INTRODUCTION TO MICROPEOCESSOR

MICROPROCESSOR BASICS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Consider a system which has 4 bits assigned for the opcode. What should be the size of control memory if each instruction uses 8 microoperations and the system utilizes the maximum number of instructions possible? Assume that each control word is of 13 bits and only one control word is assigned for one microoperation.Also, compute the number of bits in the microinstruction reserved for address information.
A
1024 bits, 7 bits
B
1048 bits, 8 bits
C
1664 bits, 7 bits
D
1400 bits, 8bits
E
1 kilobits, 6 bits
Explanation: 

Detailed explanation-1: -With only 4 bits for the instruction opcode, there’s a maximum of 16 different instructions, so the choice of which instructions to implement is challenging.

Detailed explanation-2: -Opcode size: It is the number of bits occupied by the opcode which is calculated by taking log of instruction set size. Operand size: It is the number of bits occupied by the operand. Instruction size: It is calculated as sum of bits occupied by opcode and operands.

Detailed explanation-3: -So having 6 bits for the opcode means only that you are able to encode up to 2^6=64 different instructions which can be interpreted in a single decode cycle.

Detailed explanation-4: -Five bits would allow 32 instructions total and 6 bits allows up to 64 instructions. Because 48 falls between 32 and 64, a 6-bit field must be used to ensure a complete set of unique binary opcodes. The opcode bit field defines the number line of opcode values. We call this number line the opcode space.

There is 1 question to complete.
Previous
Next