What the difference between prom and eprom?

some_one · May 7, 2008

what the difference between prom and eprom??

i know that prom is defined by address and data like 2^4 X 5

whats eprom then???

mgb_phys · May 7, 2008

erasable prom

madmike159 · May 7, 2008

eprom holds what ever is stored even when the power is turned off, unlike RAM which can be written but will lose data when it looses power.

dlgoff · May 7, 2008

Then there's EEPROM (electrically erasable programable read only memory).

zeitghost · May 8, 2008

The bit patterns in a PROM are defined at the time of manufacture, in the mask.

The bit patterns cannot be changed or erased.

The bit patterns in an EPROM are defined by the user using an eprom programmer.

A UVEPROM (the one with the quartz lid on the top) is erased by exposure to short wavelength UV light.

The EEPROM is an electrically erasable EPROM, where you don't need the UV to erase data.

madmike159 · May 8, 2008

I never knew UVEPROM was real. I saw it in a si-fi thing where it was used as a fail safe on a AI. Do you know how it works, does it just erase it and set everything to 0 or 1 or is it destroyed in the process?

dlgoff · May 8, 2008

madmike159 said: ↑

I never knew UVEPROM was real. I saw it in a si-fi thing where it was used as a fail safe on a AI. Do you know how it works, does it just erase it and set everything to 0 or 1 or is it destroyed in the process?

An EPROM cell is a MOS (metal-oxide-semiconductor) transistor that can be switched on by trapping an electric charge permanently on its gate electrode. This is done by a PAL programmer. The charge remains for many years and can only be removed by exposing the chip to strong ultraviolet light in a device called an EPROM eraser.

http://en.wikipedia.org/wiki/Programmable_logic_device" [Broken]