Chapter: Digital Principles and System Design : Memory and Programmable
Logic
Important Short Questions and Answers: Memory and
Programmable Logic
Digital Principles and System Design - Memory and Programmable Logic - Important Short
Questions and Answers: Memory and Programmable Logic
1. List basic types of programmable logic devices.
Read only memory Programmable logic Array Programmable Array Logic
2. Explain ROM
A read only memory (ROM) is a device that includes both the decoder and the OR
gates within a single IC package. It consists of n input lines and m output lines.
Each bit combination of the input variables is called an address. Each bit
combination that comes out of the output lines is called a word. The number of
distinct addresses possible with n input variables is 2n.
3. Define address and word:
In a ROM, each bit combination of the input variable is called on address. Each bit
combination that comes out of the output lines is called a word.
4. State the types of ROM
. Masked ROM.
. Programmable Read only Memory
. Erasable Programmable Read only memory.
. Electrically Erasable Programmable Read only Memory.
5. What is programmable logic array? How it differs from ROM?
In some cases the number of don’t careditionsconis excessive, it is more
economical to use a second type of LSI component called a PLA. A PLA is similar
to a ROM in concept; however it does not provide full decoding of the variables
and does not generates all the minterms as in the ROM.
6. Explain PROM.
, PROM (Programmable Read Only Memory)
It allows user to store data or program. PROMs use the fuses with material like
nichrome and polycrystalline. The user can blow these fuses by passing around 20
to 50 mA of current for the period 5 to 20μs.The blowing of fuses is called
programming of ROM. The PROMs are one time programmable. Once
programmed, the information is stored permanent.
7. Explain EPROM.
EPROM (Erasable Programmable Read Only Memory)
EPROM use MOS circuitry. They store 1’s andas a0’spacket of charge in a
buried layer of the IC chip. We can erase the stored data in the EPROMs by
exposing the chip to ultraviolet light via its quartz window for 15 to 20 minutes. It
is not possible to erase selective information. The chip can be reprogrammed.
8. Explain EEPROM.
EEPROM (Electrically Erasable Programmable Read Only Memory) EEPROM
also use MOS circuitry. Data is stored as charge or no charge on an insulated layer
or an insulated floating gate in the device.
EEPROM allows selective erasing at the register level rather than erasing all the
information since the information can be changed by using electrical signals.
9. What is RAM?
Random Access Memory-Read and write operations can be carried out.
10. What is programmable logic array? How it differs from ROM?
In some cases the number of don’t care conditions is excessive, it is more
economical to type of LSI component called a PLA. A PLA is similar to a ROM in
concept; however it does not provide full decoding of the variables and does not
generates all the minterms as in the ROM.
11. What is mask - programmable?
With a mask programmable PLA, the user must submit a PLA program table to the
manufacturer.
12. What is field programmable logic array?
Logic
Important Short Questions and Answers: Memory and
Programmable Logic
Digital Principles and System Design - Memory and Programmable Logic - Important Short
Questions and Answers: Memory and Programmable Logic
1. List basic types of programmable logic devices.
Read only memory Programmable logic Array Programmable Array Logic
2. Explain ROM
A read only memory (ROM) is a device that includes both the decoder and the OR
gates within a single IC package. It consists of n input lines and m output lines.
Each bit combination of the input variables is called an address. Each bit
combination that comes out of the output lines is called a word. The number of
distinct addresses possible with n input variables is 2n.
3. Define address and word:
In a ROM, each bit combination of the input variable is called on address. Each bit
combination that comes out of the output lines is called a word.
4. State the types of ROM
. Masked ROM.
. Programmable Read only Memory
. Erasable Programmable Read only memory.
. Electrically Erasable Programmable Read only Memory.
5. What is programmable logic array? How it differs from ROM?
In some cases the number of don’t careditionsconis excessive, it is more
economical to use a second type of LSI component called a PLA. A PLA is similar
to a ROM in concept; however it does not provide full decoding of the variables
and does not generates all the minterms as in the ROM.
6. Explain PROM.
, PROM (Programmable Read Only Memory)
It allows user to store data or program. PROMs use the fuses with material like
nichrome and polycrystalline. The user can blow these fuses by passing around 20
to 50 mA of current for the period 5 to 20μs.The blowing of fuses is called
programming of ROM. The PROMs are one time programmable. Once
programmed, the information is stored permanent.
7. Explain EPROM.
EPROM (Erasable Programmable Read Only Memory)
EPROM use MOS circuitry. They store 1’s andas a0’spacket of charge in a
buried layer of the IC chip. We can erase the stored data in the EPROMs by
exposing the chip to ultraviolet light via its quartz window for 15 to 20 minutes. It
is not possible to erase selective information. The chip can be reprogrammed.
8. Explain EEPROM.
EEPROM (Electrically Erasable Programmable Read Only Memory) EEPROM
also use MOS circuitry. Data is stored as charge or no charge on an insulated layer
or an insulated floating gate in the device.
EEPROM allows selective erasing at the register level rather than erasing all the
information since the information can be changed by using electrical signals.
9. What is RAM?
Random Access Memory-Read and write operations can be carried out.
10. What is programmable logic array? How it differs from ROM?
In some cases the number of don’t care conditions is excessive, it is more
economical to type of LSI component called a PLA. A PLA is similar to a ROM in
concept; however it does not provide full decoding of the variables and does not
generates all the minterms as in the ROM.
11. What is mask - programmable?
With a mask programmable PLA, the user must submit a PLA program table to the
manufacturer.
12. What is field programmable logic array?
