FCR Function Control. 0x40000800 0x00 0x400 registers FCR Register 0. 0x00 read-write USB_CLK_SEL USB External Core Clock Select. 16 1 sys Generated clock from system clock. 0 dig Digital clock from a GPIO. 1 QSPI0_FNC_SEL SPI0 Function Select. 17 1 hirc High speed 96MHz oscillator. 0 ext_clk External clock input. 1 I2C0_SDA_FILTER_EN I2C0 SDA Pad Deglitcher enable. 20 1 dis Deglitcher disabled. 0 en Deglitcher enabled. 1 I2C0_SCL_FILTER_EN I2C0 SCL Pad Deglitcher enable. 21 1 dis Deglitcher disabled. 0 en Deglitcher enabled. 1 I2C1_SDA_FILTER_EN I2C1 SDA Pad Deglitcher enable. 22 1 dis Deglitcher disabled. 0 en Deglitcher enabled. 1 I2C1_SCL_FILTER_EN I2C1 SCL Pad Deglitcher enable. 23 1 dis Deglitcher disabled. 0 en Deglitcher enabled. 1