Using the SSC PLL Block

The SSC PLL block lets you configure the spread-spectrum clocking PLL.

In the Base tab, specify the clock output frequency, instance name, and choose the resource.

Important: The SSC PLL block uses a MIPI D-PHY TX resource. You cannot use the same MIPI TX resource for a MIPI DPHY TX block and the SSC PLL. (You use the resource for one or the other.)

Reference Clock Settings

The SSC PLL reference clock can come from the FPGA core, a GPIO, or from a PLL clock output. You select the clocks using the Reference Clock Source Type drop-down box:

  • core—The reference clock comes from the FPGA core. Specify the clock signal name in the Reference Clock box.
  • gpio—The PLL reference clock comes from an external pin. The GUI display which GPIO resource to use.
    Note: In this mode, a GPIO block with a mipi_clkin connection type must generate the reference clock. The software displays which resource you can use (and the instance name if you have created it).
    1. Add a GPIO block.
    2. Enter the instance name.
    3. Choose input as the mode.
    4. In the Input tab, choose Connection Type > mipi_clkin.
    5. In the Resource Assigner, assign the GPIO to the resource shown in the SSC PLL's Base tab.
  • pll—The reference clock comes from a PLL clock output. The GUI shows which PLL to use. See Using the PLL Block for steps to create the PLL block.

Control / Status Settings

If you are using the spread-spectrum feature of the PLL, turn on the Enable Spread Spectrum Clock (SSC) option. Then, set the frequency and amplitude for the spread spectrum clock.

Choose whether the SSC PLL's output clock connects to a GCLK or RCLK.

Optionally, you can change the default pin names for the block.