UHCI quick send configuration register
| SINGLE_SEND_NUM | This register is used to specify the single_send register. |
| SINGLE_SEND_EN | Set this bit to enable single_send mode to send short packet. |
| ALWAYS_SEND_NUM | This register is used to specify the always_send register. |
| ALWAYS_SEND_EN | Set this bit to enable always_send mode to send short packet. |