Unlocking the Secrets of ROM: What You Need to Know About This Essential Memory

ROM (Read-Only Memory):

Read-Only Memory (ROM) is a type of non-volatile memory that stores data permanently. This means that the data stored in ROM cannot be erased or changed, even when the device is powered off. ROM is typically used to store essential instructions and data that are needed for the device to function, such as the BIOS on a computer or the firmware on a router.

If a ROM contains 2k words then with the help of k address line it is possible to select any one of the word and If the length of word is n bits then output will be n bits.

There are several different types of ROM, each with its own advantages and disadvantages. Here are the most common types

MROM (Masked Read-Only Memory):

In some type of ROM the programing of the? interconnection done during the fabrication, The program we want to store in the ROM we have to provide that program to manufacturer beforehand.

In manufacturing according to the data provided by manufacturer this interconnection are programmed in the ROM.

We enable the decoder and apply valid input address the specific interconnection are selected and based on this the data is available at the output.

For e.g. If we provide the address 00000000 then first location will be selected and based on program given to the manufacturer it masked the 1 and 0 pattern and data is available at the output. This kind of ROM is called as? the Masked ROM (MROM)

During the Fabrication of the ROM the masking has be done as per the user requirement for 1s and 0s.

PROM (Programmable Read-Only Memory):

PROM is user programable ROM means after manufacturing USER can program this ROM , but user will need the special programming hardware.

all the interconnection are made already, but after programming it is possible to remove some of the interconnection.

Based on the user requirement the user can remove specific interconnection by applying high voltage at the interconnection.

Once the PROM is programmed the specific bit pattern of 1s and 0s are written once it is written it is not possible to change that pattern

EPROM (Erasable Programmable Read-Only memory):

Once it is programmed it is possible to erase the content of ROM by applying special UV light to it.

and we can reprogrammed it by special hardware. This makes EPROM more versatile than PROM, but it is also more expensive and slower to erase and reprogram.

EEPROM (Electrically Erasable Programmable Read Only Memory):

It is possible to erase the content of Rom by electrically. The advantage of this ROM is that can be erased multiple time.?

Typically erase and write operation perform on this memory is 10000 to 100000. and Its size of EEPROM is varies form few bytes to 100KB, use for storing the small amount of data.?It come with feature like it allow to write byte level information written or erase at one time.

Flash ROM:

Similarly to the EEPROM memory the flash memory can also erase and write, but unlike the EEPROM this flash memory allows the block level erasing.

• ?It size varies from MB to GB.
• Two types of Flash memories are present

NAND Flash:? It provide the good write speed but slower Read speed and it has wide range of application such as storage drives.

NOR Flash: It provide slower write speed but good Read speed and it is costly than NAND flash and it is used in? microcontroller and BIOS chips to store a program.