CS_CMD
w &= ~CS_CMD;
w |= CS_CMD;
w |= CS_CMD;
#define CS_ERROR CS_CMD(1, 0)
#define CS_RX_DATA_RECEIVED CS_CMD(2, 0)
#define CS_TX_DATA_READY CS_CMD(3, 0)
#define CS_TX_DATA_SENT CS_CMD(4, 0)