ROM Memory Types

The ROM memory, by the abbreviation of Read only memory, in Castilian means read-only memory.

This memory is the one used by electronic equipment, as in the case of computers. The information stored in this memory does not allow its modification by the user, hence its denomination.

There are currently the following classes of ROM memory:

PROM: By the acronym of Programmable Read Only memory, in Spanish programmable ROM, it is identified by being digital. In this kind of memory each of the bits is determined by a fuse, which is only possible to burn it only once. This generates that, by means of an PROM programmer, they will be programmed for only once. The PROM memory is used in situations where information needs to be transformed into all or most opportunities. It is also sought especially in that information that wants to be stored in a lasting way that does not exceed those of the ROM.

EPROM: Its acronym for Erase programmable read-only Memory, in Castilian, erasable programmable read-only ROM. This kind of ROM memory is a chip without volatility and consists of floating door transistors or FAMOS cells that are produced from the factory without any load. This memory can be programmed using an electronic device in which these voltages exceed the employees in electronic circuits. From this, the cells begin to be read as 1, before this is done as 0. This memory offers the possibility of being erased only if it is exposed to ultraviolet lights. At the time that the EPROM is programmed, it becomes non-volatile, that is, that the stored information remains there in a timeless way. However, it can be eliminated and reprogrammed with the use of high voltage levels. While they continue to be employed, they reveal some drawbacks, among them that the process of erasing the chip is always complete, ie it is not possible to choose a particular direction. On the other hand, to reprogram or delete them, they must move from their circuit and this process takes at least twenty minutes. This type of disadvantages have been surpassed by flash memories and EEPROM, so that the eproms are going into disuse in certain designs and applications.

EEPROM: Its acronym in English electrically erase programmable Read Only Memory, which means in Castilian programmable and electrically erasable ROM. This memory, as its denomination indicates it can be programmed, erased and reprogrammed electrically without the need for exposure to ultraviolet rays, for example as in EPROMs, which implies that they are non-volatile. At the same time of possessing the floating, like the aforementioned, it has a layer of oxide located in the drainage of the MOSFET cell, which facilitates that the memory manages to be erased electrically. To do this, no specific programmers or ultraviolet rays are required, it is possible to carry it out on the circuit itself. At the same time you can rewrite and delete bytes individually, and are more affordable and faster to reprogram than previous ones. The disadvantages it has in relation to the aforementioned are the density and its high costs.

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