Home > Technology, Uncategorized > Quick differences between different types of ROMs

Quick differences between different types of ROMs


ROM (Read Only Memory)

  • As the name suggests, Once programmed cannot be reprogrammed.
  •  If the data needs to be updated throw away the programmed chip and start over with a new chip.
  • Pros:
  • less costly when produced in huge volumes
  • Robust, power efficient.
  • Cons:
  • slower

PROM (Programmable Read Only Memory)

  • This also can be programmed only once.
  • This is field programmable (ie., can be programmed anywhere).
  • Economical even when produced in small quantities.

EPROM (Electronically Programmable Read Only Memory)

  • Electronically Programmable.
  • Inexpensive per chip.
  • EPROM eraser is not selective, it erases entire chip.
  • To erase it is to be placed under the UV laser for several minutes.
  • Caution: EPROM kept under the UV laser more than required time might over erase the chip making it un-usable.

EEPROM (Electrically erasable programmable read-only memory)

  • The changes for EPROM cannot be made incrementally. For any change it erases whole chip and re-writes.
  • EEPROM can erase the targeted cells through re-writing only required cells. This way it removes this biggest drawback of EPROM.
  • EEPROM can be changed 1 Byte at a time but it is very slow.
  • Flash memory overcomes the the above limitation of slowness.
  • Flash memory erases in terms of blocks of size 512 Bytes thus improving the overall performance.

References:

http://en.wikipedia.org/wiki/EEPROM

http://computer.howstuffworks.com/rom5.htm

http://www.mycomputerscience.net/2010/06/read-only-memory1.html#

Flash and EEPROM programming from Mcirochip

Advertisements
  1. No comments yet.
  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: