Important Short Questions and Answers: Digital Electronics - Memory Devices

MEMORY DEVICES

1.           What is meant by memory Expansion? Mention its limit.

The memory expansion can be achieved in two ways: by expanding word size and expanding memory capacity.

Limitations:

1.           Memory capacity upto 16Mbytes.

2.           24 address lines and 16 data lines.

2.           What are the advantages of static RAM and Dynamic Ram?

Static RAM:

·              Access time is less.

·              Fast operation.

Dynamic Ram

·              It consumes less power.

·              Cost is low.

3.           What is difference between PAL and PLA?

PLA:

^Ø Both AND and OR arrays are programmable and Complex

^Ø      Costlier than PAL

PAL:

^Ø      AND arrays are programmable OR arrays are fixed

^Ø      Cheaper and Simpler

4.           Implement the exclusive or function using ROM.

·              Can implement multi-input/multi-output logic functions inside of ROM.

·              Data outputs are the logic functions and the address lines are the logic function inputs.

·              We create a ROM Table to store the logic functions.

·              When an input (or address) is presented, the value stored in the specified memory location appears at the data outputs.

·              Each data output represents the correct value for its logic function

5.           Compare Dynamic RAM with Static RAM.

·              Static Ram is very costly.

·              Dynamic Ram is cheaper.

·              Static Ram contains Transistors.

·              Dynamic Ram contains Capacitors.

·              Static Ram is used in L1 and L2 cache.

·              Dynamic Ram is used in system RAM.

6.           Mention few applications of PLA and PAL.

·              Implement combinational circuits

·              Implement sequential circuits

·              Code converters

·              Microprocessor based systems

7.           What are the different types of programmable logic devices?

·              PROM

·              PLA

·              PAL

·              GAL

8.           Draw the structure of a static RAM cell.

9.           List the advantages of PLDs.

·              low and fixed (two gate) propagation delays (typically down to 5 ns),

·              simple,

·              low-cost (free),

·              design tools.

10.      What is PAL?

PAL is programmable array logic, PAL consists of a programmable AND array and a fixed OR array with output logic.

11.      What is access time and cycle time of a memory?

Access time is the maximum specified time within which a valid new data is put on the data bus after an address is applied.

Cycle time is the minimum time for which an address must be held stable on the address bus in read cycle.

12. Implement a 2-bit multiplier using ROM.

13.      How the memories are classified?

It is classified into two types:

·              volatile

·              non-volatile memory

14.      Draw the logic diagram of a static RAM cell and Bipolar cell.

15.    What is volatile and non-volatile memory?

The memory which cannot hold the data when power is turned off is known as volatile memory.

The memory which can hold the data when power is turned off is known as non-volatile memory

16.    Give the advantages of RAM.

·              Read and write the data.

·              Data is accessed by using address of the memory location.

·              Higher speed.