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Electronics and Communication Engineering - Digital Electronics

Exercise : Digital Electronics - Section 1
16.
The access time of a word in 4 MB main memory is 100 ms. The access time of a word in a 32 kb data cache memory is 10 ns. The average data cache bit ratio is 0.95. The efficiency of memory access time is
9.5 ns
14.5 ns
20 ns
95 ns
Answer: Option
Explanation:

Access time = 0.95 x 10 + 0.05 x 100.

17.
The expression Y = pM (0, 1, 3, 4) is
POS
SOP
Hybrid
none of the above
Answer: Option
Explanation:

This is product of sums expression.

18.
An 8 bit DAC has a full scale output of 2 mA and full scale error of ± 0.5%. If input is 10000000 the range of outputs is
994 to 1014 μA
990 to 1020 μA
800 to 1200 μA
none of the above
Answer: Option
Explanation:

10000000 = 128, 11111111 = 255

If there is no error, output = = 1004μA.

Maximum error =

Hence range of output 994 to 1014 μA.

19.
Decimal 43 in hexadecimal and BCD number system is respectively.
B2, 01000011
2B, 01000011
2B, 00110100
B2, 01000100
Answer: Option
Explanation:

(43)10 = (2B)16

(43)10 = (01000011)2 .

20.
The circuit of the given figure realizes the function
Y = (A + B) C + DE
Y = A + B + C + D + E
AB + C +DE
AB + C(D + E)
Answer: Option
Explanation:

or

Y = (A + B)C + DE.

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