BS/EN 62680-1-2-2017 pdf download.Universal serial bus interfaces for data and power Part 1-2: Common components — USB Power Delivery specification.
Port Pair remains In Power Delivery Mode until the Port Pair Is Detached, there is a Hard Reset or the Source removes power (except during a Power Role Swap or Fast Role Swap when the initial Source removes power in order to for the new Source to apply power).
An Explicit Contract is negotiated by the process of the Source sending a set of Capabilities. from which the Sink is required to request a particular capability and then the Source accepting this request.
An Implicit Contract is the specified level of power allowed in particular states (i.e. during and after a Power Role Swap or Fast Role Swap). Implicit Contracts are temporary; Port Pairs are required to immediately negotiate an Explicit Contract.
Each Provider has a Local Policy, governing power allocation to its Ports. Sinks also have their own Local Policy governing how they draw power. A System Policy can be enacted over LJSB that allows modification to these local policies and hence management of overall power allocation in the system.
When PD Capable devices are Attached to each other, the DFPs and UFPs initially default to standard USB Default Operation. The DFP supplies vSafesV and the UFP draws current in accordance with the rules defined by (USB 2.O, (IJSB 3.11, (USH Type-C l.2j or (USBRC 1.21 specifications. After Power Delivery negotiation has taken place power can be supplied at higher, or lower, voltages and higher currents than defined in these specifications. It is also possible to perform a Power Role Swap or Fast Role Swap to exchange the power supply roles such that the DFP receives power and the UFP supplies power, to perform a Data Role Swap such that the DFP becomes the UFP and vice-versa and to perform a VCONN Swap to change the end supplying VCONN to the cable.
Prior to an Explicit Contract the Source can discover the capabilities of the Attached cable assembly. This is important for (USB Type-C 1.21 where 5A cabling is marked as well as other details of the cable assembly such as the supported speed. Cable discovery occurs on initial Attachment of a Port Pair, before an Explicit Contract has been established where the DFP is the Source. It Is also possible to carry out cable discovery after a Power Role Swap or Fast Role Swap prior to establishing an Explicit Contract, where the UFP is the Source and an Implicit Contract is in place.
Once an Explicit Contract is In place only the DFP is permitted to communicate with the Attached cable assembly. This communication can consist of discovering capabilities but may also include discover of SVIDs, Modes and the entering/exiting of Modes supported by the cable assembly.
2.2 Section Overview
This specification contains the following sections:
SOP Communication is used for Port to Port communication between the Source and the Sink. SOP Communication is recognized by both Port Partners but not by any intervening Cable Plugs. SOP Communication takes priority over other SOPS Communications since it is critical to complete power related operations as soon as possible. Message sequences relating to power are also allowed to interrupt other sequences to ensure that negotiation and control of power is given priority on the bus.
24.4 SOP’ISOP” Communication with Cable Plugs
SOP’ Communication is recognized by electronics in one Cable Plug which is the Cable Plug that detected VCONN at Attach (see (IISB Type-C 1.2J). SOP” Communication can also be supported when SOP’ Communication is also supported. SOP” Communication is recognized by the electronics In the Cable Plug that did not detect VCONN at Attach.
The Vconn Source is the DFP/Source at attach although all of these roles can later be swapped using PD messaging.
SOP Communication between the Port Partners is not recognized by the Cable Plug. Figure 2-2 outlines the usage of SOP Communications between a VCONN Source (DFP/UFP) and the Cable Plugs.
All SOP Communications take place over a single wire (CC). This means that the SOP Communication periods must be coordinated to prevent important communication from being blocked. For a product which does not recognize SOP/SOP’ or SOP” Packets, this will look like a non-idle channel, leading to missed packets and retries. Communications between the Port Partners take precedence meaning that communications with the Cable Plug can be interrupted, but will not lead to a Soft or Hard Reset.
When no Contract or an Implicit Contract is In place (e.g. after a Power Role Swap or Fast Role Swap) the Source (which can be either the DFP or UFP but must also be the VCONN Source) can communicate with a Cable Plug using SOP’ Packets in order to discover its characteristics (see Figure 2-2). During this phase all communication with the Cable Plug Is initiated and controlled by the Source which acts to prevent conflicts between SOP Packets. The Sink does not communicate with the Cable Plug, even if it is the DFP, and Discards any SOP Packets received.
When an Explicit Contract is in place the VCONN Source (either the DFP or the UFP) can communicate with the Cable Plug(s) using SOP/SOP” Packets (see Figure 2-2). During this phase all communication with the Cable Plug is initiated and controlled by the VCONN Source which acts to prevent conflicts between SOP Packets. The Port that is not the VCONN Source does not communicate with the Cable Plug and does not recognize any SOP/SOP” Packets received. Only the DFP, when acting as a VCONN Source, is allowed to send SOP* In order to control the entry and exiting of Modes and to manage Modal Operation.BS/EN 62680-1-2-2017 pdf download.