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A vertical microprogrammed CU supports  256 instructions. The system is using 8 flag conditions and contains 48 control signals. Each instruction on an avg requires 16 micro-operations. What is the approx. size of control memory in bytes?

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  As vertical micro programmed we required 6bits to represent 48 control signals

The system is using 8 flag conditions which required 3bits

A vertical microprogrammed CU supports  256 instructions and each instruction on an avg requires 16 micro-operations then total no of micro operations is = 256*16=4096 which require 12bits to represent.

Branch(0 bit) Flag (3bits) Control signal (6bits) Control Memory Address (12bits)

the size of the control word = 3+6+12= 21bits /8 =2.625 Byte

the approx. size of control memory in bytes = 2^12 * 2.625 bytes =10752 Bytes

3 votes
3 votes

Vertical microprogrammed CU supports  256 instructions,

The system is using 8 flag conditions,

contains 48 control signals. ,

Each instruction on an avg requires 16 micro-operations. ,


CU support 256 instructions where each instruction requires 16 MO $\therefore$ there will be $256 * 16 = 4096 \ CW$
Now one Control word structure will be something like this :
 

3 For flags 6 For signal (Vertical) 12 For addressing next CW

$\therefore 21 \  bits \ for \  one \ CW$
 


Size of Control MEmory = $4096 * 21 = 86016bits \ or\ 10752Bytes$

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