XADC_COMMAND
WR4(sc, XADCIF_CMDFIFO, XADC_COMMAND(XADC_CMD_WRITE, reg, data));
WR4(sc, XADCIF_CMDFIFO, XADC_COMMAND(XADC_CMD_READ, reg, 0));
WR4(sc, XADCIF_CMDFIFO, XADC_COMMAND(XADC_CMD_NOP, 0, 0));