FLASH MEMORY

The MT28F004B3 (x8) and MT28F400B3 (x16/x8) are nonvolatile, electrically block-erasable (flash), programmable memory devices containing 4,194,304 bits organized as 262,144 words (16 bits) or 524,288 bytes (8 bits). Writing or erasing the MT28F004B3 and MT28F400B3 is done with either a 3.3V or 5V VPP voltage, while all operations are performed with a 3.3V VCC. Due to process technology advances, 5V VPP is optimal for application and production programming. These devices are fabricated with Micron's advanced 0.18µm CMOS floating-gate process.

The MT28F004B3 and MT28F400B3 are organized into seven separately erasable blocks. To ensure that critical firmware is protected from accidental erasure or overwrite, the MT28F004B3 and MT28F400B3 feature a hardware-protected boot block. Writing or erasing the boot block requires either applying a super-voltage to the RP# pin or driving WP HIGH in addition to executing the normal write or erase sequences. This block may be used to store code implemented in low-level system recovery. The remaining blocks vary in density and are written and erased with no additional security measures.