Hi all, I am trying to add a custom RFNoC block and my block runs on different clocks(not the default ones). So I followed the instructions from the FAQ page in RFNoC wiki of deriving clocks from the available clocks - https://kb.ettus.com/RFNoC_Frequently_Asked_Questions#How_do_I_add_a_clock_with_a_different_frequency.3F But when I add the parameters in block YAML, it added new ports to my *rfnoc_block_myblock* module, which is not what I expected. My intention was to derive 2 clocks from the rfnoc_chdr_clk and use it inside my block. For this I added the clock IP module (instantiated) in the noc_shell_myblock, because this is where the CDC FIFOs are there. So, with this method the generated clock just stays inside my block and won't be available outside to it. Maybe the steps described in the FAQ might not be the right way to go about with my requirement? I am not sure. Also, I tried not adding the YAML parameters of the clocks for my block. This worked to the point where the implementation of the entire design failed with WNS of -0.8ns on the new derived clock I added. I also got a few Critical warnings for the clocks I added, not sure if it is related somehow or if I can ignore it - *TIMING-4#1 Critical WarningInvalid primary clock redefinition on a clock tree Invalid clock redefinition on a clock tree. The primary clock x4xx_core_i/rfnoc_image_core_i/b_myblock_3/noc_shell_myblock_i/clk_wiz_chdr_200_125_inst/inst/clk_in_chdr is defined downstream of clock clk200 and overrides its insertion delay and/or waveform definition. * I followed this thread ( https://www.mail-archive.com/usrp-users%40lists.ettus.com/msg14663.html) to add IPs of my clock module that I generated with with Vivado IP catalog and copied the *.xci, .v* and other generated files into the path/to/module/rfnoc/fpga/myblock/ip/ and changed the Makefile and block YAML definitions like the example given in the example Gain block. I checked the timing summary report and I found that the violation happens in the derived clock that connects to one of my blocks. I was able to build the IP by itself when I was testing it for viability. Any tips or leads in adding custom derived clocks to the design would be super helpful and thank you all for maintaining such a nice community!! -J

Hey Jons, if you're generating and using a custom clock within your RFNoC block, then there is nothing from RFNoC that you need. Unless you're exporting your clock, you don't need to declare it anywhere. However, you *do* need to follow all the Vivado/Digital design guidelines for adding clocks (i.e., stuff that is unrelated to RFNoC specifically). If you need to inject custom constraints, you can do that from your block YAML. Just add .xdc files in the same directory where your HDL is, and refer to them in the YAML like we do here: https://github.com/EttusResearch/rfnoc-oot-blocks/blob/main/rfnoc/blocks/aurora.yml --M On Sun, Jul 27, 2025 at 7:28 PM Jons <jonsdeburn@gmail.com> wrote: > Hi all, > I am trying to add a custom RFNoC block and my block runs on different > clocks(not the default ones). So I followed the instructions from the FAQ > page in RFNoC wiki of deriving clocks from the available clocks - > https://kb.ettus.com/RFNoC_Frequently_Asked_Questions#How_do_I_add_a_clock_with_a_different_frequency.3F > But when I add the parameters in block YAML, it added new ports to my > *rfnoc_block_myblock* module, which is not what I expected. My intention > was to derive 2 clocks from the rfnoc_chdr_clk and use it inside my block. > For this I added the clock IP module (instantiated) in the > noc_shell_myblock, because this is where the CDC FIFOs are there. So, with > this method the generated clock just stays inside my block and won't be > available outside to it. Maybe the steps described in the FAQ might not be > the right way to go about with my requirement? I am not sure. > > Also, I tried not adding the YAML parameters of the clocks for my block. > This worked to the point where the implementation of the entire design > failed with WNS of -0.8ns on the new derived clock I added. I also got a > few Critical warnings for the clocks I added, not sure if it is related > somehow or if I can ignore it - > > > > *TIMING-4#1 Critical WarningInvalid primary clock redefinition on a clock > tree Invalid clock redefinition on a clock tree. The primary clock > x4xx_core_i/rfnoc_image_core_i/b_myblock_3/noc_shell_myblock_i/clk_wiz_chdr_200_125_inst/inst/clk_in_chdr > is defined downstream of clock clk200 and overrides its insertion delay > and/or waveform definition. * > > I followed this thread ( > https://www.mail-archive.com/usrp-users%40lists.ettus.com/msg14663.html) > to add IPs of my clock module that I generated with with Vivado IP catalog > and copied the *.xci, .v* and other generated files into the > path/to/module/rfnoc/fpga/myblock/ip/ and changed the Makefile and block > YAML definitions like the example given in the example Gain block. > > I checked the timing summary report and I found that the violation happens > in the derived clock that connects to one of my blocks. I was able to build > the IP by itself when I was testing it for viability. > > Any tips or leads in adding custom derived clocks to the design would be > super helpful and thank you all for maintaining such a nice community!! > -J > > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-leave@lists.ettus.com >