Test: Semiconductor Memories - 1 - Electronics and Communication Engineering (ECE) MCQ

Dynamic RAM (DRAM)

 

Concept:

EEPROM

EEPROM is a PROM that is that can be erased and reprogrammed using an electrical charge.

• EEPROM is a user-modifiable ROM.
• It also has a limited life - that is, the number of times it can be reprogrammed is limited to tens or hundreds of thousands of times.
• These can be programmed using special external programming signals.
• These are organized as an array of floating gate transistors.

NOTE: A special form of EEPROM is flash memory, which uses normal PC voltages for erasure and reprogramming.

SRAM

Data is stored in the transistors and requires a constant power flow.

• Because of the continuous power supply, SRAM doesn’t need to have the refreshing circuit.
• It is more expensive and holds fewer data per unit volume. So, used in cache.
• The power consumption of the SRAM is dependent on how frequently it is used.

DRAM

SDRAM (synchronous DRAM) is a generic name for various kinds of DRAM that are synchronized with the clock speed that the microprocessor is optimized for. 

• The clock frequency of the microprocessor is half of the frequency of the crystal oscillator used.
• In the DRAM operation of the external pin, the interface is maintained by an externally applied clock signal.
• For DRAM continuous refreshing clock cycles are required for the retention of data stored.

MARAM

It stores the data in magnetic form instead of electric charges.

• It uses far less power than other RAMs so it is good for portable devices.
• Magnetoresistance is the tendency of a material (often ferromagnetic) to change the value of its electrical resistance in an externally-applied magnetic field.
• On account of the rising demand for fast, scalable, low power consuming, and non-volatile memory devices, especially in the automotive, enterprise storage, and aerospace and defense sectors, the global market for magnetoresistive RAM (MRAM) is likely to gain significant impetus over the forthcoming years.

1. NIC is used to connect a computer to an Ethernet network.
2.The card usually contains the protocol control firmware and the Ethernet controller needed to support Medium Access control (MAC).
3. A MAC address is given to a network adapter. It is a hardware into the computer Network interface card (NIC) and is also unique.
4. It is a six-byte or 48-bit address that uniquely identifies the Ethernet-based connection.

Concept:

Memory Chips:

• The number of address pins is related to the number of memory locations.
• The data pins are typically bi-directional in read-write memories. The number of data pins is related to the size of the memory location.

Given that, 

Address pins= 24 (is related to the number of memory locations)

Data pins= 16 (It is related to the size of the memory location)

So For 'N-Bits' address pins, the number of locations that will accommodate is 2^N.

So For '24-Bits' address pins, the number of locations that will accommodate is 224.

Hence the correct answer is 224.

The conversion of memory is given below.

1 TB = 1024 GB

1 GB = 1024 MB

1 MB = 1024 kB

1 kB = 1024 Byte

1 Byte = 8 bits

Concept:

• EPROM and EEPROM is a type of ROM.
• Data in ROM can be accessed randomly and hence EPROM and EEPROM are random access memory.

Important Points:

• EPROM is an erasable programmable read-only memory.
• It is a non-volatile memory that means its data will be retained even when the power is turned off.
• EEPROM (electrically erasable programmable read-only memory) is a user-modifiable read-only memory (ROM) that can be erased and reprogrammed (written to) repeatedly through the application of higher than normal electrical voltage.

In a DRAM, a capacitor to store a bit of data is used along with a MOSFET (transfer device) which acts as a switch. The circuit is as shown –

In a DRAM:

• Periodic refreshing is required.
• The information is stored in a capacitor.
• Both read and write operations cannot be performed simultaneously.

Programmable logic device (PLD):

It is an IC with a large number of logic gates, which is programmed by software to perform a specific digital logic function. And it can be changed according to the application.

Examples: PLA, PAL, FPLA, PROM, GAL, FPGA, etc.

Fixed functional ICS:

It is an ICs in a compact form that is designed to perform for fixed logic applications and it can not be changed after manufacture.

Examples: IC-555, IC-741, Johnson counter, full adder, parallel adder, etc.

Advantages of PLD over fixed functional ICs:

So, the correct option is D.

Concept:

Address line: An address line is basically refers to a physical connection between a CPU/Chipset and memory. They specify which addresses to access in memory. When there are k address lines, then 2k memory word can be accessed.

Data line: Data lines provides the information to be stored in memory. It represents the number of bits in the word.

Calculation:

Here, it is given that memory unit size = 256 bytes

2^k = 256

k = 8

1. A bit is the smallest unit of storage.
2. A bit stores just a 0 or 1.
3. Computers are designed to store data and execute instructions in bit multiples called bytes.
4. One byte is equal to 8 bits.

EPROM (Erasable programmable read-only memory):

• EPROM stands for erasable programmable read-only memory.
• EPROM is a nonvolatile kind of memory.
• If ultraviolet rays are exposing (Mercury –vapor light) to the EPROM chip, then this chip will release stored charge. The stored content in that EPROM chip will be lost or erased.