dualROM

Dualrom is a term used in the field of embedded memory to describe a memory architecture in which firmware or data is stored in two separate ROM banks. The two banks share a common address and data bus, while a bank-select signal or boot control selects which bank is active for execution or read during normal operation. The design aims to provide redundancy, easy firmware updates, or a dual-boot capability without requiring dual-ported memory. In typical configurations, a small controller chooses between bank 0 and bank 1 at reset or during a boot sequence, possibly guided by a nonvolatile flag or a bootloader setting. Some systems implement a form of dual-boot by placing a primary image in one bank and a validated backup in the other; a watchdog or integrity check can ensure the active bank remains consistent.

Implementation considerations include memory size, address mapping, and the mechanism to lock down ROM contents. Additional features may include a parity or CRC across banks, or the ability to switch banks after post-boot for firmware recovery. Applications are common in embedded systems requiring high reliability, such as automotive, consumer electronics with over-the-air updates, and industrial controllers; dualrom can reduce the risk of bricking during firmware updates.

Limitations include increased silicon area, higher cost, and potential complexity in the boot process. The term is not universally standardized and may be used informally to describe any two-bank ROM scheme rather than a formal specification.