mrom vs prom

First of all I'd check the spelling... its the first time I've heard of an mrom?

A prom is programmable read only memory but an mrom...????

John.

mrom =mask read only memory

Oh.... I've always referred to them as just rom.... oh well thanks anyway!!

John.

I also had never heard of "MROM" until today.

The first Proms I worked with were stuffed with fusible links. You set up each address and then blew out the links for the appropriate word out. These were like 82S123 and 82S129 made by TI. If you blew the wrong link, your rom was instant garbage. They had EPROMS at the time, but they wouldn't work at 20 MHz clock speeds.

EPROMS (which worked at 1 or 2 MHz) were erasable. They were erased via an ultraviolet light. These Proms had a glass window over the actual chip to let the UV light through. After programming, you always put tape or plastic dots over the window to keep the chip from being erased by ambient light. I still have a PROM eraser around here somewhere though I havent seen it in years.

They then came out with EEPROMS which were Electronic Erasable PROMS. This got rid of the UV light.

a masked rom is made by the chipmaker and cannot be changed. a programmable ROM is what is used to develop the mrom. They are erasable and can be reprogrammed again and again until you end up with the final program. You then get the chip maker to make you 20 million iof the ships for the end use. For small runs mroms are not cost effective and the erasable ones are used

I never went to the prom. I didn't go past my 11th year. Mrom is a now failed energy company known for bilking billions in false earnings and......what? Mrom.....huh...? Oh my mistake. Apparently that is Enron. Oh well.

cr3