A RAM chip has a capacity of 1024 words of 8 bits each (1K × 8). The number of 2 × 4 decoders with enable line needed to construct a 16K × 16 RAM from 1K × 8 RAM is
(A) 4
(B) 5
(C) 6
(D) 7
Answer: (B)
Explanation:
RAM chip size = 1k ×8[1024 words of 8 bits each] RAM to construct =16k ×16 Number of chips required = (16k x 16)/ ( 1k x 8) = (16 x 2) [16 chips vertically with each having 2 chips horizontally] So to select one chip out of 16 vertical chips, we need 4 x 16 decoder. Available decoder is 2 x 4 decoder To be constructed is 4 x 16 decoder Hence 4 + 1 = 5 decoders are required.