Mask ROM is a type of read-only memory, or ROM, that is masked off during production. "Mask" refers to parts of an integrated circuit, a thin electronic circuit for processing data, that is covered with opaque plates called photomasks.
These plates contain transparencies, or holes, to allow light in certain areas while blocking light in others to create distinctive patterns. Mask work, comprising a process known as photolithography, primarily serves as a sort of intellectual property protection, reserving reproduction of the product to the integrated circuit manufacturer.
Like other types of ROM, mask ROM cannot enable the user to change the data stored in it. If it can, the process would be difficult or slow. Thus, ROM is primarily distributed as firmwire—software, or coded instructions—permanently stored in ROM. Firmwire is particularly suitable for field programmability, which involves programming into the electronic device without taking it apart.
More specifically, this type of ROM is sub-categorized as semiconductor memory. This term is used for data storage that is placed on a semiconductor-based integrated circuit, or a chip built on a piece of material that possesses electrical conductivity.
Some users rely on mask ROM for storing the finalized code of their projects. When projects are being developed, data can be stored using non-volatile memory. This is a type of computer memory that can store data even with the lack of power or a power source.
Examples of non-volatile memory include erasable programmable read-only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM). Some micro-controllers, or the tiny computer on the integrated circuit responsible for controlling the electronic device on which it is installed, have non-volatile memory for development purposes and mask ROM for finalized code.
