Flash Memory Chips

NAND Flash vs. NOR Flash: How Flash Memory Works

Flash memory stores data by trapping electrons in a floating-gate transistor within each flash memory cell, then reading the resulting shift in threshold voltage. NAND flash arranges cells in series for high density and lower cost per bit, making it the standard choice for solid-state drives and bulk storage. NOR flash arranges cells in parallel, giving each cell its own connection to the bit line. That trades density for faster random-access reads and direct code execution, which is why NOR flash is more common in embedded flash memory for firmware and bootloaders. NAND flash and NOR flash suit different jobs: capacity versus fast code execution.

Serial Flash Memory vs. Parallel Flash Memory

Serial flash memory, most often SPI NOR flash or QSPI flash memory, connects to a host over as few as four pins and trades some speed for board space. Parallel flash memory uses a full address and data bus for faster access, at the cost of more pins and PCB area. Most new designs default to serial NOR flash for its smaller footprint, while a NAND flash controller manages larger memory storage.