Question

A horizontal micro-programmed control unit has 81-signals every micro-instruction contain 3 fields, one control word, one MUX select to select one of 16 inputs and one 15-bits address field. There are 50 types of instructions CPU can support. Each instruction requires 10 micro-operations to be executed. Size of control memory required to store all microinstructions (in bits) is________.

• A. 50000
• B. 40000
• C. 20000
• D. 60000

Answer 1

The correct option is A 50000

Micro-insturction

$\begin{array}{ccc}\text{Control word}& \text{MUX select}& \text{Address}\end{array}$
81 bits 4 bits 15 bits =100 bits

Number of micro-instruction required $=50\times 10=500$

Size of control memory $=500\times 100=50000bits$