ARM-core combined with Phison's proprietary micro-controller.
However, there is a dark side. Because these tools are publicly available, unscrupulous sellers use them to manipulate drive firmware. They can program the PS2251-68 to report a larger capacity than the physical memory holds (e.g., a 32GB chip reporting as 512GB). This has led to a plague of "fake flash" drives flooding the market. phison ps225168ps2268