TTE_Bridge

Interfaces and Buses / TimeTriggeredEthernet / TTE_Bridge

Block Name: TTE_Bridge

Code Location: VisualSim/actor/lib/networking/tte/TTE_Bridge

Table of Contents

Description
Block Dependencies
Examples
Tutorial
Parameters

Description

TTEthernet Bridge take care of partitioning among time-triggered, rate-constrained, and best-effort Ethernet traffic. High-priority time-triggered messages are routed through the bridge according to a predefined schedule with pre-definable constant latency and jitter in the sub-microsecond range. Rate-constrained messages are passed on according to the respective guaranteed bandwidth reservations. Finally, best-effort Ethernet messages are forwarded when bandwidth is available.

Based on the contents of the Type Field of an incoming message, the Bridge decides whether an incoming message is a standard Ethernet (BE) message or TT Ethernet message. BE Ethernet messages and TT Ethernet messages are handled differently by the bridge.
Arriving standard Ethernet (BE) messages are stored in an BE-message queue of the bridge. The message, which is at the end of the message queue, is forwarded to the specified receiver address whenever the outgoing channel to this receiver is free. If an outgoing BE message is in the way of an incoming TT message, then the bridge immediately clears the channel (preempts the BE message) for the pending TT message. Immediately after the TT message has terminated, the bridge retransmits the (previously preempted) BE message, and, if the transmission was successful, releases the message buffer occupied by this message for a new incoming BE message. This autonomous TTEthernet protocol mechanism uses any bandwidth that becomes free for the immediate transmission of BE-messages. It optimizes the throughput without any need for an explicit scheduling action and thus simplifies the schedule design and the system operation.
Arriving TT Ethernet messages are not stored in the bridge. They are delayed by the bridge for a defined number of µseconds (clearance delay, which is the time needed to clear the transmission path in the case of a preempted BE message) and then forwarded in to the addressed receivers.

If the TTE Bridge block is configured as compression master, then the compression master calculate an averaging value from the relative arrival times of these protocol control frames and send out a new protocol control frame in a second step. This new protocol control frame is then also sent to synchronization clients.

TTE_Bridge is provided with an option to consider itself as a compression master or not. Compression master consoliats all the timing signals sent by Synchronization masters and then it sends the message back to all the nodes connected to it on the timing.  This ensure that all devices and switches on the network have the same clock.

Block Dependencies:

TTE Bridge must be used with TTE_Node, TTE_Config, TTE_Setup and TTE_Traffic blocks

Examples:

1. TTE Example System with three Sources and One Destination with Single Bridge
2. TTE Example System with Multi-Bridge
3. TTE Example System with two Redundant Connections

Tutorial:

A detailed tutorial of TTEthernet networke System exploration is available in this document.

Parameters: