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What sets the JESD parameters, HDL build or devicetree?

Category: Software
Product Number: AD9081

I am using an AD9081-FMCA-EBZ on a ZCU102.

I see all of the example device trees on github. Here is an excerpt from the file "zynqmp-zcu102-rev10-ad9082-204c-txmode22-rxmode23-sc1.dts"

// ad9081_204b_txmode_0_rxmode_1: 204C use case with Subclass 0,
// Med. lane rate, using gearbox and PRGOGDIV
//     * 1Txs / 1Rxs per MxFE
//     * DAC_CLK = 11.52GSPS
//     * ADC_CLK = 3.84GSPS
//     * Tx I/Q Rate: 960 MSPS (Interpolation of 12x1)
//     * Rx I/Q Rate: 960 MSPS (Decimation of 4x1)
//     * DAC JESD204B: Mode 22, L=2, M=2, N=N'=12
//     * ADC JESD204B: Mode 23, L=2, M=2, N=N'=12
//     * DAC-Side JESD204B Lane Rate: 11.88Gbps
//     * ADC-Side JESD204B Lane Rate: 11.88Gbps

// HDL Synthesis Parameters:
// JESD_MODE=64B66B \
// RX_RATE=12 \
// RX_PLL_SEL=2 \
// TX_RATE=12 \
// TX_PLL_SEL=2 \
// REF_CLK_RATE=180 \
// RX_JESD_M=2 \
// RX_JESD_L=2 \
// RX_JESD_S=4 \
// RX_JESD_NP=12 \
// TX_JESD_M=2 \
// TX_JESD_L=2 \
// TX_JESD_S=2 \
// TX_JESD_NP=12

The documenting of the HDL build parameters inside the devicetree file, communicates to me, that the HDL build sets the JESD parameters, and the devicetree should match those. That would indicate that the HDL build sets the JESD parameters. The devicetree simply matches what was used during the HDL build.

Am I reading too much into that comment in the devicetree file?

Is it possible to change the JESD parameters at boot time, using the devicetree?

Top Replies

    •  Analog Employees 
    Mar 8, 2024 in reply to don@qiqsystems +1 verified

    Hi  ,

    So, in order to use other set of JESD parameters, you will need to build HDL sources again with the new parameters (make <parameters>) and also to re-build the devicetree with the…

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  • Not sure I understand the question. Of course both end of the Link need to use the same parameters.

    I put the parameters there for my own convenience. So whenever I want to build that bitstream again I can copy paste those....

    You can change the devicetree, rebuilt it and use the revised to during boot.

    -Michael

  • I was searching for a good way to ask the question, so thanks for your patience.

    What I gather from your response, is that the JESD parameters that are used when the HDL is built, must also be the same in the devicetree.

    I cannot change the JESD parameters in the devicetree to change how the HDL is working.

  • Hi  ,

    So, in order to use other set of JESD parameters, you will need to build HDL sources again with the new parameters (make <parameters>) and also to re-build the devicetree with the new parameters modified inside it. And then just to replace the output files (BOOT.BIN and system.dtb) on SD Card and reboot.

    Of course, parameters values used to build HDL must match the ones set in devicetree.

    Thanks,

    Stefan

Reply
  • Hi  ,

    So, in order to use other set of JESD parameters, you will need to build HDL sources again with the new parameters (make <parameters>) and also to re-build the devicetree with the new parameters modified inside it. And then just to replace the output files (BOOT.BIN and system.dtb) on SD Card and reboot.

    Of course, parameters values used to build HDL must match the ones set in devicetree.

    Thanks,

    Stefan

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