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What is ROM ? Explain the types of ROM.OR Explain the semi conductor based ROM memories.

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By Dipali Umre

Read Only Memory (ROM):

  • Definition: It’s a type of memory in computers and electronic devices designed to store data permanently or data that doesn’t change often. It’s also known as non-volatile memory, meaning it retains its content even when the power is turned off.

Types of ROM:

  1. Programmable Read Only Memory (PROM):
    • Description: Can be programmed only once using a special device called a PROM programmer.
    • Process: Uses high voltages to create or destroy internal links within the chip, making it a one-time programmable memory.
  2. Erasable Programmable Read Only Memory (EPROM):
    • Description: Can be erased by exposure to strong ultraviolet light and then reprogrammed.
    • Process: Requires UV light for erasing and a higher than usual voltage for rewriting.
    • Endurance: Can endure over 1000 cycles of erasing and reprogramming.
    • Identification: Often has a quartz window for UV light, covered with a label after programming.
  3. Electrically Erasable Programmable Read Only Memory (EEPROM):
    • Description: Similar to EPROM but allows electric erasure and rewriting without removing from the device.
    • Process: Entire contents can be electrically erased and then rewritten, making it more convenient.
    • Speed: Slower writing process compared to reading from ROM or writing to RAM.
  4. Mask Programming:
    • Description: Done by the company during the fabrication process of the unit.
    • Procedure: Customer provides the desired truth table, and the ROM is fabricated accordingly.
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