USB Endpoint Buffer Configuration register
| RESERVED | Reserved. Fixed to zero because the control endpoint zero is fixed to single-buffering for each physical endpoint. |
| BUF_SB | Buffer usage: This register has one bit per physical endpoint. 0: Single-buffer. 1: Double-buffer. If the bit is set to single-buffer (0), it will not toggle the corresponding EPINUSE bit when it clears the active bit. If the bit is set to double-buffer (1), HW will toggle the EPINUSE bit when it clears the Active bit for the buffer. |
| RESERVED | Reserved |