UM2191
USB
Type-C and Power Delivery
DocID030479 Rev 2
15/55
The V
CONN
is systematically assigned to the free CC pin of the receptacle after a connection
is established: the CC pins can be monitored to verify a valid Rp/Ra connection and then
the V
CONN
supply is routed by the source to the checked pin.
Since all the full-featured Type-
C™ cables are reversible, both CC pins in the receptacle
must be able to assume the role of CC and V
CONN
on cable insertion.
1.11
Alternate modes and billboard device class
The USB Power Delivery specification supports alternate mode (Alt Mode) to transfer high-
speed data over Type-
C™ cables using protocols like:
High-Definition Multimedia Interface (HDMI)
DisplayPort (DP)
Peripheral Component Interconnect Express (PCI Express)
Ethernet over twisted pair (Base-T Ethernet)
Mobile High-Definition Link (MHL)
The adoption of alternate mode lets Type-C hosts and devices incorporate additional
functionality, exploiting USB PD structured vendor defined messages (Structured VDMs) to
manage typical display controller selection mechanisms: discover, enter and exit.
As alternate modes do not traverse the USB hub topology, they may only be used between
a directly connected host and device.
Structured VDMs may also be used for re-assignment of the pins that the USB Type-C
connector exposes.
Figure 8: Pins available for reconfiguration on the plug of the full-featured cable
The following figure shows the pins available for reconfiguration with direct connect
applications. There are three more pins because this configuration is not limited by the
cable wiring.
Figure 9: Pins available for reconfiguration on the receptacle for direct connect applications
Where no equivalent USB functionality is implemented, the device must provide a USB
interface exposing a USB billboard device class to identify the device. This is not required
for non-user facing modes (e.g., diagnostic modes).