GPIO Intel® FPGA IP User Guide: Intel® Arria® 10 and Intel® Cyclone® 10 GX Devices

ID 683136
Date 7/15/2021

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Input Path

The pad sends data to the input buffer, and the input buffer feeds the delay element. After the data goes to the output of the delay element, the programmable bypass multiplexers select the features and paths to use. Each input path contains two stages of DDIOs, which are full-rate and half-rate.
Figure 2. Simplified View of Single-Ended GPIO Input Path

  1. The pad receives data.
  2. DDIO IN (1) captures data on the rising and falling edges of ck_fr and sends the data, signals (A) and (B) in the following waveform figure, at single data rate.
  3. DDIO IN (2) and DDIO IN (3) halve the data rate.
  4. dout[3:0] presents the data as a half-rate bus.
Figure 3. Input Path Waveform in DDIO Mode with Half-Rate Conversion

In this figure, the data goes from full-rate clock at double data rate to half-rate clock at single data rate. The data rate is divided by four and the bus size is increased by the same ratio. The overall throughput through the GPIO IP core remains unchanged.

The actual timing relationship between different signals may vary depending on the specific design, delays, and phases that you choose for the full-rate and half-rate clocks.

Note: The GPIO IP core does not support dynamic calibration of bidirectional pins. For applications that require dynamic calibration of bidirectional pins, refer to the related information.

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