LVDS Tunneling Protocol and Interface (LTPI) IP User Guide: Agilex™ 3 and Agilex™ 5 FPGAs and SoCs
ID
844310
Date
8/15/2025
Public
1. Overview
2. Configuring and Generating the IP
3. Simulating the IP
4. Validating the IP
5. Troubleshooting and Debugging Issues
6. Appendix A: Functional Description
7. Appendix B: Registers
8. Document Revision History for the LVDS Tunneling Protocol and Interface (LTPI) IP User Guide: Agilex™ 3 and Agilex™ 5 FPGAs and SoCs
1.4.4.1. Link Detect and Link Speed Selection Frames
1.4.4.2. Link Detect Frame
1.4.4.3. Link Speed Frame
1.4.4.4. Advertise, Configure, and Accept Frames
1.4.4.5. Advertise Frames
1.4.4.6. Configure Frame
1.4.4.7. Accept Frame
1.4.4.8. LTPI Operational Frames
1.4.4.9. Default I/O Frame
1.4.4.10. Default Data Frame
1.4.6.2. Link Configuration
After the link training phase is completed, the Link Configuration phase begins by operating at the target frequency selected during the link speed stage.
The main goals of this phase are to switch to the operational link frequency, exchange LTPI feature capabilities, enable the selected operational configuration, and transition to the operational mode.
The link configuration phase consists of three states:
- Advertise
- Configure
- Accept
Advertise
The advertise state is the initial phase when the link switches from the base frequency to the operational frequency after the link speed state was done. In this state, both SCM and HPM start sending the advertise frame, which transmitted in both directions. After switching to the operational frequency, the LVDS RX needs to readjust to the beginning of the frame, like the link detect stage. This stage is divided into two parts:
- Frame alignment—Locks onto the beginning of the frame by identifying the comma symbol and verifying the CRC (requiring at least three Frames with correct CRC to proceed).
- Advertise part—Frames are used to interpret the LTPI capabilities of the other side.
Figure 10. LTPI Link Advertise State
Configure and Accept
The SCM sends the configure frames to HPM. If the HPM receives a configure frame that matches its capabilities, it responds with an accept frame. Once SCM receives this matching accept frame, it transitions to the next state by sending the first operation frame on the link.
Figure 11. LTPI Link Configure and Accept State