USB Type-C® Nomenclature and Features
Contents
Although the USB Type-C® specification was released about the same time as the USB 3.1 specification, the two specifications are distinct from each other. Type-C introduced a new cable and some enhanced USB capabilities. USB 3.1 (also referred to as 3.1 Gen 2) introduces the 10 Gbps transfer speed.
USB Type-C is compatible with USB 2.0, USB 3.0 and USB 3.1 devices. Type-C offers new naming conventions for some USB elements.
Naming Conventions
The well-known names of host and device have been replaced in the USB Type-C specifications with Downstream Facing Port (DFP) and Upstream Facing Port (UFP). Type-C provides the ability for the roles of the elements to change.
Type-C New Features
Reversible Cable
Type-C USB defines a cable with 24 pins. The symmetrical connectors on each end of the cables are identical. Type-C cables can be easily plugged into a DFP or a UFP without the user having to adjust the orientation of the plug. Type-C systems are designed to work seamlessly regardless of which end of the cable is plugged into a device, and whether or not the cable is oriented correctly (i.e., there is no wrong way to plug in a Type-C cable).
See the "Type-C Cables and Connectors" page for more details on how the system detects and adjusts for cable orientation.
Backward Compatibility with previous USB protocols
Type-C cabling contains the four USB 2.0 signals as well as the additional signals required to implement USB 3.0 and 3.1. USB 2.0 devices can be connected to Type-C cables and work as-is. The additional capabilities and signals of Type-C cables will go unused. The Type-C specification provides for three types of cables:
- Passive
- Electronically Marked Cable Assembly (EMCA)
- Managed Active Powered Cable
Passive Type-C cables are required to carry USB 2.0 signals and be capable of supplying 60W of power.
See the "Type-C Cables and Connectors" page for more details on Type-C cables and backward compatibility.
Alternate Mode of Operation
Alternate Mode allows third-party protocols to be transmitted over the USB Type-C cable. This mode is negotiated on a port-by-port basis using the Power Delivery Protocol. See the "Type-C Alternate Mode" page for details on re-configuring Type-C pins.
Enhanced Power Delivery Negotiation
USB Power Delivery allows power configuration of a USB connection to be dynamically modified. The default 5 V VBUS can be modified up to 20 V. The maximum power delivered by a port can also be modified up to 100 W (with an appropriate Electronically Marked Type-C cable). See the "USB Power Delivery" page for details on the configurable power delivery options of USB.
Data Role Switching
Data roles (DFP and UFP) can be dynamically switched using the Power Delivery Protocol.
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