7738 DSI Protocol

774On the transmitter side of a DSI Link, parallel data, signal events, and commands are converted in the

775Protocol layer to packets, following the packet organization documented in this section. The Protocol layer

776appends packet-protocol information and headers, and then sends complete bytes through the Lane

777Management layer to the PHY. Packets are serialized by the PHY and sent across the serial Link. The

778receiver side of a DSI Link performs the converse of the transmitter side, decomposing the packet into

779parallel data, signal events and commands.

780If there are multiple Lanes, the Lane Management layer distributes bytes to separate PHYs, one PHY per

781Lane, as described in Section 6. Packet protocol and formats are independent of the number of Lanes used.

7828.1 Multiple Packets per Transmission

783In its simplest form, a transmission may contain one packet. If many packets are to be transmitted, the

784overhead of frequent switching between LPS and High-Speed Mode will severely limit bandwidth if

785packets are sent separately, e.g. one packet per transmission.

786 The DSI protocol permits multiple packets to be concatenated, which substantially boosts effective

787bandwidth. This is useful for events such as peripheral initialization, where many registers may be loaded

788with separate write commands at system startup. Figure 9 illustrates multiple packets being sent separately,

789and as concatenated packets in a single HS transmission.

790In HS Mode, time gaps between packets shall result in separate HS transmissions for each packet, with a

791SoT, LPS, and EoT between packets. This constraint does not apply to LP transmissions.

7948.2 Packet Composition

795The first byte of the packet, the Data Identifier (DI), includes information specifying the length of the

796packet. For example, in Video Mode systems in a display application the logical unit for a packet may be

797one horizontal display line. Command Mode systems send commands and an associated set of parameters,

798with the number of parameters depending on the command type.

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