WB_SD_CSR
val = wb_read(wb, WB_SD_CSR);
wb_write(wb, WB_SD_CSR, val);
wb_write(wb, WB_SD_CSR, 0);
val = wb_read(wb, WB_SD_CSR);
wb_write(wb, WB_SD_CSR, val);
rv = (wb_read(wb, WB_SD_CSR) & WB_CSR_CARD_PRESENT) ? 1 : 0;
rv = (wb_read(wb, WB_SD_CSR) & WB_CSR_WRITE_PROTECT) ? 1 : 0;