4. Build a 2K x 4-bit RAM using any number of 1K x 4-bit RAMs below. The block y

Question

4. Build a 2K x 4-bit RAM using any number of 1K x 4-bit RAMs below. The block you use to represent 2K x 4-bit RAM should have a 11-bit wide address input, a 4-bit wide data input, a 1-bit RW input, and a 4-bit wide data output. (Hint: A[9:0]: 10-bit address input, Din[3:0]: 4-bit data input, CS: 1-bit chip select control signal, R/W: 1-bit read/write control signal, Dout[3:0]: 4-bit data output.) 10A9:0] 1KX 4 Din(3:0] RAM Dout[B:o R/W CS Answer: A90] 9:0] 10 1KX 4 Din(3.0] RAM Dout[3:0) Din 3.0] CS R/W 1-40-2 Docoder 9:01 1Kx4 Dout 3:0l Din(3:01 RAM CS R/W R/W A[I0]

Explanation / Answer

given Answer is the solution for the given problem.

Since we need to construct 2Kx4 using 1Kx4.

therefore numer of chis needed : 2K/1K =2 chips of size 1Kx4

since for 2K memory numer of address bits = Log2(2K) =11, so 11 bits are for addreess.

since for 1k memory number of address bits : Log2(1K)=10. so left most 10 bits from 11 bits should be connected to 1Kx4 memory.

since two memory are connect vertically so, lets talk about address space:

Address generated by 2Kx4 memory :

00000000000

......................

......................

0FFFFFFFFFF

100000000000

.......................

.......................

FFFFFFFFFFF

here you can see that half of the address space has 11th bit is 0 and half of address space has 11th bit 1, so if we use 11th bit as Chip select line, so all address spce can be generated.

thats why if 11th bit is 0 then 1st chip is select so

00000000000

......................

......................

0FFFFFFFFFF adress are generated, same for 11th bit=1 then 2nd chip is slected and respective address line are generated.

Since for read or write operation, chip should be selected then only data of chip is coming to the data bus, thats why read/write signal is ANDED with CS line.

at output side since 4 bit data is generated, thats need to multiplexed to get data from any of the chip.

Please give thumbs up, thanks

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