PLL in Cora Z7-07S

[simmerj]

Hello,

I'm trying to make a PLL on the Cora Z7-07S to create a clock speed around 200MHz, but I don't know how. The Reference Manual confirms that it's possible to go up to 625MHz, but there is no example code or instructions. The Lattice FPGAs I worked with before had their own functions for plls, so I'm at a loss for how to do one from scratch.

 

Thank you

[zygot]

For ZYNQ you have a lot of ways to create derived clocks.

In the PS there are PLLs that run the interfaces, cores and external memory controller. You can use the GUI block design tools to do this. These PS clocks can be exported to the PL either in Vivado IP or as external connections into your PL logic.

In the PL you have the same PLL/MMCM clock generators for creating custom clocks.

There's no instructions. There are Xilinx user manuals for ZYNQ devices, Series 7 Clocking resource, and of course descriptions on ho wot use the tools. There are also tutorials that make it a bit simpler to grasp. They all can be found by using the Document Navigator that gets installed with Vivado.

I recommend not trusting the Digilent user manuals but using the schematics and Xilinx documentation, including the device datasheet for information about maximum clock rates for your board. Trust but verify as POTUS Ron would say.

Unfortunately, ZYNQ devices are kind of a separate world from the other FPGA logic devices even though the PL resources are the same as the Series 7 devices. This just makes finding relevant information a bit harder.

Edited July 25, 2023 by zygot

[artvvb]

Hi @simmerj

You can modify the Zynq PS configuration's "Clock Configuration" settings to add a 200 MHz clock. The Clocking Wizard IP can be used to configure MMCMs and PLLs - there are some catches here if you're feeding it from a Zynq PS fclk, you should make sure to set the input clock to "No buffer". If you're adding a PLL into custom HDL, refer to the Language Templates in the app for copy-pastable instantiation templates, though this is a complex option that requires close attention to datasheets.

Thanks,

Arthur