Read only memory(ROM)| Definition &Types
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Read only memory(ROM)| Definition &Types
ROM is the memory that stores data permanently, that is, it can retain data even when the computer system is powered off. Data from this type of memory can be easily read but not changed. ROM is usually used in devices such as calculators, laser printers, etc. ROM does not allow random access of data rather it allows sequential access of data. It is less expensive than RAM and other storage devices like magnetic disks etc. ROMs are divided into four types, which are as follows:
★ Programmable ROM (PROM),
★ Erasable PROM (EPROM),
★ Electrically Erasable PROM (EEPROM),
★Flash ROM,
Programmable ROM
Programmable ROM (PROM) is a memory chip with which data can be written only once. Data is stored permanently on this chip, that is, once a program is written in PROM, it cannot be erased or destroyed. To write data to a PROM chip, a device known as a PROM programmer or PROM burner is required. The process of writing data to the chip is called PROM burning. PROM is reliable and stores data permanently without any changes to it. It is commonly used in video games and electronic dictionaries.Erasable PROM
Erasable PROM (EPROM) is a type of ROM in which data can be effaced or spoiled using ultraviolet light (UL). Erasable ROM provides the facility to change the content of data, ie, it can be reprogrammed. It contains floating gate transistors, which have the ability to retain electrical charge even when the computer system is powered off. It also facilitates the storage of data for a long period of time.Electrically erasable PROM
Electrically erasable PROM (EEPROM) is a type of ROM in which data can be effaced or spoiled by exposing it to an electric charge. It has the ability to retain stored data even when the computer system is powered off. It stores data permanently but allows us to make changes to the data by erasing it with the help of electrical charges. In this type of memory, data can be written or erased only one byte at a time, which makes it very slow.Flash ROM
Flash ROM is a type of EEPROM that stores data using floating-gate transistors, which can store electrical charge for longer periods of time than ordinary transistors. This memory is mainly used to store mobile phone memory cards, digital cameras and iPod data. The data stored in the Ili Flash ROM memory can be easily transferred using transmission mediums such as data cable, Bluetooth and infrared technology. For example, we can transfer the data stored in the flash ROM memory of the mobile phone to the computer memory using a data cable. We can easily erase data stored in flash ROM memory and reprogram this type of memory. Flash ROM has faster data read speed than any other type of ROM. It uses non-volatile memory cells to store data.Flash ROM memory cells are made of floating-gate transistors. A single-level cell (SLC) stores only one bit of data, whereas a multi-level cell (MLC) provides storage facilities greater than bytes.Two types of flash ROM memory are as follows:
NAND flash
In NAND flash or NAND gate flash memory, each cell behaves like a metal (semiconductor field effect transistor (MOSFET), which has two gates to amplify an ele signal.NOR gate flash or NOR flash
Nor flash provides the facility to write data or information using tunnel injection. It can be defined as the process of inserting electrons into an electrical conductor using a layer of electrical insulator. It also provides the facility to delete tunnel release instructions.FAQs
1.What are the 4 examples of ROM?
Here are 4 examples of ROMs:1.PROM
2.EPROM
3.EEPROM
4.Flash ROM,
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