SDAA410 June   2026 AM2611 , AM2612 , AM2612-Q1 , AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1 , AM263P2 , AM263P2-Q1 , AM263P4 , AM263P4-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 The Challenge of Determinism in Robotics
    2. 1.2 Why standard ethernet fails for real-time communication
      1. 1.2.1 Head-of-Line Blocking
      2. 1.2.2 Lack of Time Synchronization
      3. 1.2.3 No Traffic Scheduling
    3. 1.3 Time-Sensitive Networking (TSN) based proposed solution
      1. 1.3.1 What is TSN?
      2. 1.3.2 IEEE 1588 (802.1AS gPTP - generalized Precision Time Protocol)
      3. 1.3.3 IEEE 802.1Q (VLAN)
      4. 1.3.4 IEEE 802.1Qbu/Qbr (IET - Interspersing Express Traffic / Frame Preemption)
      5. 1.3.5 IEEE 802.1Qbv (EST - Enhancements for Scheduled Traffic)
      6. 1.3.6 CPSW Specific hardware features
  5. 2Sample Use Cases: Distributed Motion Control in Robotics
    1. 2.1 Representative scenario
    2. 2.2 Network Topology Requirements
      1. 2.2.1 Why Daisy-Chain?
      2. 2.2.2 Real world applications of daisy chain ethernet solutions
    3. 2.3 Communication Requirements
    4. 2.4 Test Implementation
  6. 3System Overview and Architecture
    1. 3.1 Hardware Architecture
      1. 3.1.1 AM261x LaunchPad
      2. 3.1.2 CPSW Sub-System overview:
    2. 3.2 Software architecture
  7. 4Sample Implementation
    1. 4.1 Standard Ethernet + CPSW InterVLAN routing
      1. 4.1.1 What is Inter-VLAN Routing
      2. 4.1.2 How This Implementation leverages Inter-VLAN Routing:
      3. 4.1.3 Test-1 Benchmarks
    2. 4.2 Integrating gPTP Time Synchronization (IEEE802.1AS)
      1. 4.2.1 What is PTP time synchronization?
      2. 4.2.2 How this implementation uses GPTP time synchronization
      3. 4.2.3 Test-2 Benchmarks
    3. 4.3 Integrating VLAN (IEEE802.1Q)
      1. 4.3.1 What is VLAN?
      2. 4.3.2 How this implementation leverages VLAN
      3. 4.3.3 Test-3 benchmarks
    4. 4.4 Integrating IET Frame Preemption (IEEE802.1Qbu/Qbr)
      1. 4.4.1 What is IET (Interspersed Express Traffic)?
      2. 4.4.2 How this implementation leverages IET
      3. 4.4.3 Test-4 Benchmarks
    5. 4.5 Integrating EST scheduling (IEEE802.1Qbv)
      1. 4.5.1 What is EST?
  8. 5Conclusion
  9. 6Challenges and Debug considerations
    1. 6.1 Network Topology Verification
    2. 6.2 Traffic Flow Analysis
    3. 6.3 Host Port Traffic Monitoring
    4. 6.4 PHY Link Management
    5. 6.5 Packets not forwarded to next node
    6. 6.6 Error Handling and Retries
    7. 6.7 High latency or Jitter for high priority packets
    8. 6.8 gPTP not synchronizing
  10. 7References

4.4.1 What is IET (Interspersed Express Traffic)?

The IEEE 802.1Qbu and IEEE 802.3br standards work in tandem to define the Interspersing Express Traffic (IET) frame preemption mechanism. This technology reduces latency for time-critical data in Time-Sensitive Networking (TSN) applications. When a high-priority express packet arrives at a network switch while a low-priority, best-effort packet is already being sent, the switch temporarily pauses the transmission of the low-priority frame. The urgent traffic is immediately sent across the wire. Once the time-critical data has completely cleared the queue, the switch resumes the transmission of the fragmented lower-priority frame right from where it left off. This hardware-level optimization prevents massive data frames from blocking time-sensitive control communication. It eliminates the need for large, inefficient guard bands and ensures deterministic performance in automated environments like industrial robotics and automotive networks.