Mask OmniScriptum Mask ROM Paperback

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Mask ROM is a type of read-only memory whose contents are programmed by the integrated circuit manufacturer. The terminology "mask" comes from integrated circuit fabrication, where regions of the chip are masked off during the process of photolithography. It is common practice to use rewritable non-volatile memory - such as UV-EPROM or EEPROM - for the development phase of a project, and to switch to mask ROM when the code has been finalized. For example, Atmel microcontrollers come in both EEPROM and mask ROM formats. The main advantage of mask ROM is its cost. Per bit, mask ROM is more compact than any other kind of semiconductor memory. Since the cost of an integrated circuit strongly depends on its size, mask ROM is significantly cheaper than any other kind of semiconductor memory. However, the one-time masking cost is high and there is a long turn-around time from design to product phase. Design errors are costly: if an error in the data or code is found, the mask ROM is useless and must be replaced in order to change the code or data.