The XFR2VBUS supports 1 command in the command FIFO.
- 1 XOUT to define the address, data and size (on the fly). 1 Byte, 4 Byte, 32 Byte, 64 Byte and must be aligned.
- Only 1 write command can be in flight since this is VBUSP
- 1 XIN the software can see the status of write command FIFO and write data FIFO