Difference between revisions of "Read-only memory"

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(lame explination of rom's.)
 
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ROM is simply Read Only Memory.
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'''ROM''' is simply '''Read Only Memory'''.
  
Unlike [[RAM]] ROMs cannot be written to. ROMs are also typically slower then RAM.
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Unlike [[Random Access Memory|RAM]], ROMs cannot be written to. At one point, ROMs are also typically slower than RAM.
  
 
ROMs come in several flavors:
 
ROMs come in several flavors:
  
 
== PROM ==
 
== PROM ==
PROM's can be programed ONCE then read many times.  If there is any mistakes in the PROM code, the entire chip must be disgarded.  While PROMs can be read in a normal board, they need to be programmed in a special device.
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PROMs can be programmed ONCE then read many times.  If there are any mistakes in the PROM code, the entire chip must be discarded.  While PROMs can be read in a normal board, they need to be programmed in a special device (since programming them often requires special [[voltage]]s).
  
 
== EPROM ==
 
== EPROM ==
  
EPROMs can be erased after they have been programmed.  Normally there is a small window in the chip in which exposure to UV light will erase the EPROMs programming.  EPROM's need to be programmed in a special programmer.
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[[Image:M27C512 EPROM.jpg|150px|right|An EPROM]]
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EPROMs can be erased after they have been programmed.  Normally there is a small window in the chip in which exposure to UV light will erase the EPROMs programming.  EPROMs also need to be programmed in a special programmer.
  
 
== EEPROM ==
 
== EEPROM ==
  
EEPROMS can be erased electronically, and reprogrammed. While similar to [[Flash Memory]], however they need to be erased & programmed in a special programmer.
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EEPROMS can be erased electronically, and re-programmed, usually through the application of higher than normal voltage. In modern EEPROMS this is generated internally. Unlike EPROMs, EEPROMS can be re-written in-circuit.
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==External links==
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* [http://madrona.ca/e/corerope/index.html Core Rope & Woven-Wire Memory Systems]
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[[Category: Computer Basics]]

Latest revision as of 11:58, 26 April 2022

ROM is simply Read Only Memory.

Unlike RAM, ROMs cannot be written to. At one point, ROMs are also typically slower than RAM.

ROMs come in several flavors:

PROM

PROMs can be programmed ONCE then read many times. If there are any mistakes in the PROM code, the entire chip must be discarded. While PROMs can be read in a normal board, they need to be programmed in a special device (since programming them often requires special voltages).

EPROM

An EPROM

EPROMs can be erased after they have been programmed. Normally there is a small window in the chip in which exposure to UV light will erase the EPROMs programming. EPROMs also need to be programmed in a special programmer.

EEPROM

EEPROMS can be erased electronically, and re-programmed, usually through the application of higher than normal voltage. In modern EEPROMS this is generated internally. Unlike EPROMs, EEPROMS can be re-written in-circuit.

External links