How many 256x8 RAM chips are needed to provide a memory capacity of 4096 bytes?
a) How many bits will each memory address contain?
b) How many address lines must go to each chip?
c) How many lines must be decoded for the chip select inputs? Specify the size of the decoder.
a)
4096/256=16 bits.
From the given question the information provided is :
Size of each Ram chip is : 256X8{meaning: each chip contains 256
memory words and each word length is 8-bits}
Total memory capacity is: 4096 bytes
To find number of chips : Total Memory capacity / Size of each Ramchip
: 4096/256=16
So 16 ram chips needed to provide a memory capacity of 4096 bytes
Ram 0 Ad0-Ad255 |
Ram 1 Ad256-Ad511
|
Ram 2 Ad512-Ad767
|
Ram 15 Ad3584-Ad3839
|
Ram 16 Ad3840-Ad4095
|
1) How many bits will each memory address lines contains?
Sol) The total Memory capacity is : 4096 = 212
So each memory address contains 12-bits
2) How many address lines must go to each chip line ?
Sol) To select the chip we need 4-bits from the memory address of
12-bits because we have 16 ram chips, to select each ram chip it needs minimum of 4 bits .
Example :
1 |
0 |
1 |
1 |
0 |
1 |
0 |
1 |
1 |
0 |
1 |
0 |
( Chip ) ( Address from each chip )
: from the above figure the given address specifies that it select’s chip 11(1011) and the address bit is 90(01011010)
3) How many line must be decoded for the chip select input specify the size of the decoder?
Sol) we have 16 Ram chips so we need 4 –to--16 decoder to select one Ram from 16 Ram’s for each address .
Post the discussion to improve the above solution.