Uniform Sector

Standard and Dual Serial Flash

GD25WD40C/20C

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4. DEVICE OPERATION

SPI Mode

Standard SPI

The GD25WD40C/20C features a serial peripheral interface on 4 signals bus: Serial Clock (SCLK), Chip Select (CS#),

Serial Data Input (SI) and Serial Data Output (SO). Both SPI bus mode 0 and 3 are supported. Input data is latched on the

rising edge of SCLK and data shifts out on the falling edge of SCLK.

Dual SPI

The GD25WD40C/20C

supports Dual Output operation when using the “Dual Output Fast Read” (3BH) commands.

These commands allow data to be transferred to or from the device at twice the rate of the standard SPI. When using the

Dual Output command the SI and SO pins become bidirectional I/O pins: IO0 and O1.