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- What is a PEROM ?
- Skeleton Man
February 25, 2009, 1:08 am
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Re: What is a PEROM ?
These are the types I'm familiar with.
1) Mask ROM. These are used for permanent read-only
memory. There is a one time fee, to make the mask for
the ROMs. Typically, you might do this, if you needed
100,000 identical devices, like firmware for something.
For smaller production runs, use something else.
2) Fuseable ROM. Its been many years since I used these.
These can be programmed once, and use something
like Titanium-Tungsten. In the lab, I burned up $3000
worth of these, while doing product development. Great
fun when the boss finds out. They're not reprogrammable.
Now starts the devices based on Flash technologies.
3) OTP - this would be a flash memory which is one
time programmable. It would allow, for example,
a custom serial number to be placed in each component,
as well as, say, some firmware. These might be used
for the SPD chip on memory DIMMs, as an example. No
erase options available.
4) EPROM - eraseable programmable read only memory.
By means of a UV window and a UV light source, the
device can be erased and returned to the all 1's state.
More common in the 32 pin DIP era. Many happy hours
spent with the UV light and trays of chips.
5) EEPROM - electrical eraseable EPROM. No window on this
one, it can be erased electrically, with the right
voltage applied. These would be used on motherboards.
Your "PEROM" appears to be another way of stating (4).
Until you mentioned it, I didn't even know anyone was
using a term like that. It's always been "EPROMs" with
Both (4) and (5) have limits to the number of write/erase
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