SIE control register
| START_TRANS | Host: Start transaction |
| SEND_SETUP | Host: Send Setup packet |
| SEND_DATA | Host: Send transaction (OUT from host) |
| RECEIVE_DATA | Host: Receive transaction (IN to host) |
| STOP_TRANS | Host: Stop transaction |
| PREAMBLE_EN | Host: Preable enable for LS device on FS hub |
| SOF_SYNC | Host: Delay packet(s) until after SOF |
| SOF_EN | Host: Enable SOF generation (for full speed bus) |
| KEEP_ALIVE_EN | Host: Enable keep alive packet (for low speed bus) |
| VBUS_EN | Host: Enable VBUS |
| RESUME | Device: Remote wakeup. Device can initiate its own resume after suspend. |
| RESET_BUS | Host: Reset bus |
| PULLDOWN_EN | Host: Enable pull down resistors |
| PULLUP_EN | Device: Enable pull up resistor |
| RPU_OPT | Device: Pull-up strength (0=1K2, 1=2k3) |
| TRANSCEIVER_PD | Power down bus transceiver |
| EP0_STOP_ON_SHORT_PACKET | Device: Stop EP0 on a short packet. |
| DIRECT_DM | Direct control of DM |
| DIRECT_DP | Direct control of DP |
| DIRECT_EN | Direct bus drive enable |
| EP0_INT_NAK | Device: Set bit in EP_STATUS_STALL_NAK when EP0 sends a NAK |
| EP0_INT_2BUF | Device: Set bit in BUFF_STATUS for every 2 buffers completed on EP0 |
| EP0_INT_1BUF | Device: Set bit in BUFF_STATUS for every buffer completed on EP0 |
| EP0_DOUBLE_BUF | Device: EP0 single buffered = 0, double buffered = 1 |
| EP0_INT_STALL | Device: Set bit in EP_STATUS_STALL_NAK when EP0 sends a STALL |