GENERAL DESCRIPTION
   The GD25R256D (256M-bit) Serial flash supports the standard Serial Peripheral Interface (SPI), and supports the Dual/Quad SPI: Serial Clock, Chip Select, Serial Data I/O0 (SI), I/O1 (SO), I/O2, and I/O3 . The Dual I/O data is transferred with speed of 208Mbits/s and the Quad I/O & Quad output data is transferred with speed of 416Mbits/s.