Ciarcia, Steve (1981). Ciarcia's Circuit Cellar > 자유게시판

Learn-solely memory (ROM) is a type of non-unstable Memory Wave used in computer systems and other digital gadgets. Data saved in ROM cannot be electronically modified after the manufacture of the Memory Wave Workshop gadget. Read-only memory is useful for storing software program that is rarely changed in the course of the life of the system, also referred to as firmware. Software program functions, resembling video video games, for programmable devices might be distributed as plug-in cartridges containing ROM. Strictly speaking, read-only memory refers to exhausting-wired memory, reminiscent of diode matrix or a mask ROM built-in circuit (IC), that can not be electronically modified after manufacture. Though discrete circuits could be altered in principle, by the addition of bodge wires and the removal or replacement of elements, ICs can't. Correction of errors, or updates to the software program, require new gadgets to be manufactured and to replace the installed device. Floating-gate ROM semiconductor memory within the type of erasable programmable learn-only memory (EPROM), electrically erasable programmable learn-solely memory (EEPROM) and flash memory could be erased and re-programmed.

However often, this could only be carried out at relatively slow speeds, might require particular equipment to realize, and is typically solely possible a certain number of instances. The time period "ROM" is typically used to check with a ROM device containing specific software or a file with software to be stored in a writable ROM gadget. For instance, customers modifying or replacing the Android operating system describe files containing a modified or alternative operating system as "customized ROMs" after the kind of storage the file used to be written to, and they could distinguish between ROM (where software and data is stored, normally Flash memory) and RAM. ROM and RAM are important parts of a computer, each serving distinct roles. RAM, or Random Access Memory, is a temporary, volatile storage medium that loses data when the system powers down. In contrast, ROM, being non-risky, preserves its data even after the computer is switched off.

IBM used capacitor learn-only storage (CROS) and transformer learn-solely storage (TROS) to retailer microcode for the smaller System/360 models, the 360/85, and the initial two System/370 models (370/155 and 370/165). On some fashions there was additionally a writeable management retailer (WCS) for extra diagnostics and emulation support. The Apollo Steerage Pc used core rope memory, programmed by threading wires by way of magnetic cores. The best type of stable-state ROM is as previous because the semiconductor know-how itself. Combinational logic gates will be joined manually to map n-bit handle input onto arbitrary values of m-bit information output (a look-up table). With the invention of the built-in circuit came mask ROM. Mask ROM consists of a grid of word traces (the address input) and bit traces (the information output), selectively joined with transistor switches, and may signify an arbitrary look-up desk with a daily bodily structure and predictable propagation delay. Mask ROM is programmed with photomasks in photolithography during semiconductor manufacturing.