According to "AN01027 Porting the XMOS USB 2.0 Audio Reference Software onto XU208 custom hardware", Usb tranceiver use the following ports:
<Port Location="XS1_PORT_1H" Name="PORT_USB_TX_READYIN"/>
<Port Location="XS1_PORT_1J" Name="PORT_USB_CLK"/>
<Port Location="XS1_PORT_1K" Name="PORT_USB_TX_READYOUT"/>
<Port Location="XS1_PORT_1M" Name="PORT_USB_RX_READY"/>
<Port Location="XS1_PORT_1N" Name="PORT_USB_FLAG0"/>
<Port Location="XS1_PORT_1O" Name="PORT_USB_FLAG1"/>
<Port Location="XS1_PORT_1P" Name="PORT_USB_FLAG2"/>
<Port Location="XS1_PORT_8A" Name="PORT_USB_TXD"/>
<Port Location="XS1_PORT_8B" Name="PORT_USB_RXD"/>

In this case, we could don't use port 8B ( 6 physical pins actually,X0D14,X0D15,X0D16,X0D17)anymore.
Can I map XS1_PORT_8C to PORT_USB_RXD ?
If Yes, only 4 physical pins(X0D26,X0D27,X0D28,X0D29) is occupied, and I have extra 2 pins to configure as input or output ports.
Whats more, for Port 8D

1M0,1N0,1O0,1P0 is part of 8D, and is used as 1bit ports(no matter input or output), Can I usd remaining parts of 8D (8D4,8D5,8D6,8D7)as multiple-bit input/output?