LVDS Tunneling Protocol and Interface IP User Guide: Agilex™ 5 FPGAs and SoCs
ID
844310
Date
2/24/2025
Public
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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
6.1. GPIO Channel
The GPIO channel tunnels low-speed HPM and SCM GPIOs through the LTPI interface.
It sorts GPIOs into two types:
- Low latency (LL) GPIOs
- Normal latency (NL) GPIOs
It is a specific platform design decision that determines whether the GPIO falls into the LL GPIO or NL GPIO category.
Figure 29. GPIO Mapping in LTPI GPIO Channel
The LL and NL GPIO Characteristics table shows an overview of the LL and NL GPIO characteristics.
Parameter | LL GPIO | NL GPIO |
---|---|---|
Bandwidth | Each LL GPIO is assigned a specific bit in the LTPI frame with maximum bandwidth of the frame and the status of each GPIO is updated with every LTPI frame. | The maximum LTPI bandwidth is distributed across a set number of bits in the LTPI frame. These bits are shared among the NL GPIOs. Based on the equation below, updating all NL GPIOs requires N number of LTPI frames, depending on the number of NL GPIOs and the bits allocated to them in the LTPI frame. |
Number of GPIOs | Maximum of the numbers of LTPI frame bits allocated for LL GPIOs. | Maximum of the acceptable latency for NL GPIOs. Increasing the number of NL GPIOs results a higher latency. |
Figure 30. Calculating Number of LTPI Frames for Updating NL GPIOs Equation