BRDCFG4[USBOSC] and BRDCFG5[SPR] register field of Qixis device is used
to control SPI and other IP signal routing.
USBOSC:
0= SPI_CLK used as external USB REFCLK input driven with 24.000 MHz.
SPI devices are unusable in this mode.
1= SPI_CLK used as SPI clock.
SPI devices are usable in this mode. USB block is clocked from
internal sources
SPR[3:2]:
SPI_CS / SDHC_DAT4:7 Routing (schematic net CFG_SPI_ROUTE[3:2]):
00= SDHC/eMMC 8-bit
01= SD Card Rev 2.0/3.0
10= SPI on-board memory
11= TDM Riser / SPI off-board connector.
The default value is 00 if an SDCard/eMMC card is selected as the boot
device.