Intel N28F001BXB120: A Comprehensive Technical Overview of the 1-Megabit Flash Memory Chip
The Intel N28F001BXB120 stands as a significant milestone in the evolution of non-volatile memory technology. As a 1-megabit (128K x 8) flash memory chip, it encapsulated the cutting-edge of semiconductor manufacturing in its era, providing a reliable and electrically erasable solution for a wide range of applications, from PC BIOS storage to embedded systems and telecommunications equipment.
Fabricated using Intel's advanced CMOS EPROM technology, this device offered a substantial improvement over its predecessors, notably EPROMs that required ultraviolet light for erasure. The N28F001's core innovation was its ability to be erased and reprogrammed electrically in-system, dramatically simplifying the firmware update process for engineers and manufacturers. Its 128-kilobyte capacity, organized in a byte-wide architecture, was a substantial amount of storage for critical system code and data in the late 1980s and early 1990s.
A key architectural feature of this chip is its divided block structure. The memory array is not uniform; it consists of multiple 16 KB blocks, one 8 KB block, two 4 KB blocks, and one 24 KB parameter block. This design was intentional, allowing for greater flexibility. The smaller blocks were ideal for storing frequently updated data or boot code, enabling sector-by-sector erasure without affecting the entire chip. This significantly improved efficiency and longevity compared to chips requiring a full chip erase for any modification.
The device operates on a single 5-volt power supply for all functions—read, erase, and program—making it highly compatible with the standard TTL logic levels prevalent in the systems of its time. The "120" in its part number signifies a 120ns maximum access time, indicating its speed in delivering data to the system's microprocessor. Programming and erasing are managed through a command user interface (CUI). By writing specific instruction sequences into the command register, the microprocessor can control the complex internal high-voltage algorithms, thereby insulating the system designer from low-level timing complexities.
The chip features a JEDEC-standard pinout, ensuring a degree of compatibility with other manufacturers' offerings and simplifying design-in. It also includes several hardware and software data protection mechanisms. These include a programming lockout feature during power transitions and an optional software command set protection protocol to prevent accidental corruption of stored data.
In summary, the Intel N28F001BXB120 was a workhorse of early flash memory, bridging the gap between EPROM and the high-density NAND flash that would follow. Its blend of a practical density, flexible block architecture, and single-power-supply operation made it a cornerstone of embedded design for nearly a decade.
ICGOOODFIND: The Intel N28F001BXB120 is a quintessential example of first-generation NOR flash memory. Its enduring legacy lies in its robust block-oriented architecture that optimized firmware updates, its single 5V power supply compatibility that simplified system design, and its implementation of a command user interface that abstracted complex programming operations. It set a standard for reliability and flexibility for embedded code storage.
Keywords: Flash Memory, Non-Volatile Memory, Block Erase, Command User Interface, 5-Volt Operation.
