CPRI Intel® FPGA IP User Guide

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ID 683595
Date 5/19/2023
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Document Table of Contents
Document Table of Contents x
1. About the CPRI Intel® FPGA IP Core 2. Getting Started with the CPRI Intel® FPGA IP Core 3. Functional Description 4. CPRI Intel® FPGA IP Core Signals 5. CPRI Intel® FPGA IP Core Registers 6. CPRI Intel® FPGA IP User Guide Archives 7. Document Revision History for the CPRI Intel® FPGA IP User Guide
1. About the CPRI Intel® FPGA IP Core x
1.1. CPRI Intel® FPGA IP Core Supported Features 1.2. CPRI Intel® FPGA IP Core Device Family and Speed Grade Support 1.3. Intel® FPGA IP Core Verification 1.4. Resource Utilization for CPRI Intel® FPGA IP Core 1.5. Release Information
1.2. CPRI Intel® FPGA IP Core Device Family and Speed Grade Support x
1.2.1. Device Family Support 1.2.2. CPRI Intel® FPGA IP Core Performance: Device and Transceiver Speed Grade Support
2. Getting Started with the CPRI Intel® FPGA IP Core x
2.1. Installation and Licensing 2.2. Generating CPRI Intel® FPGA IP Core 2.3. CPRI Intel® FPGA IP File Structure 2.4. CPRI Intel® FPGA IP Core Parameters 2.5. Integrating Your Intel® FPGA IP Core in Your Design: Required External Blocks 2.6. Simulating Intel FPGA IP Cores 2.7. Understanding the Testbench 2.8. Running the Design Example 2.9. Compiling the Full Design and Programming the FPGA
2.1. Installation and Licensing x
2.1.1. Intel® FPGA IP Evaluation Mode
2.5. Integrating Your Intel® FPGA IP Core in Your Design: Required External Blocks x
2.5.1. Adding the Transceiver TX PLL IP Core 2.5.2. System PLL Connections for the Intel Agilex® 7 F-tile Variations 2.5.3. Adding the Reset Controller 2.5.4. Adding the Transceiver Reconfiguration Controller 2.5.5. Adding the Off-Chip Clean-Up PLL 2.5.6. Adding and Connecting the Single-Trip Delay Calibration Blocks 2.5.7. Transceiver PLL Calibration 2.5.8. Reference and System PLL Clock for your IP Design
3. Functional Description x
3.1. Interfaces Overview 3.2. CPRI Intel® FPGA IP Core Clocking Structure 3.3. CPRI Intel® FPGA IP Core Reset Requirements 3.4. Start-Up Sequence Following Reset 3.5. AUX Interface 3.6. Direct IQ Interface 3.7. Ctrl_AxC Interface 3.8. Direct Vendor Specific Access Interface 3.9. Real-Time Vendor Specific Interface 3.10. Direct HDLC Serial Interface 3.11. Direct L1 Control and Status Interface 3.12. L1 Debug Interface 3.13. Media Independent Interface (MII) to External Ethernet Block 3.14. Gigabit Media Independent Interface (GMII) to External Ethernet Block 3.15. CPU Interface to CPRI Intel® FPGA IP Registers 3.16. Auto-Rate Negotiation 3.17. Extended Delay Measurement 3.18. Deterministic Latency and Delay Measurement and Calibration 3.19. CPRI Intel® FPGA IP Transceiver and Transceiver Management Interfaces 3.20. Testing Features
3.2. CPRI Intel® FPGA IP Core Clocking Structure x
3.2.1. Example CPRI Intel® FPGA IP Core Clock Connections in Different Clocking Modes
3.4. Start-Up Sequence Following Reset x
3.4.1. Start-Up Sequence Interface Signals
3.5. AUX Interface x
3.5.1. AUX Interface Signals 3.5.2. AUX Interface Synchronization 3.5.3. Auxiliary Latency Cycles 3.5.4. Direct Interface CPRI Frame Data Format
3.14. Gigabit Media Independent Interface (GMII) to External Ethernet Block x
3.14.1. GMII Normal Mode 3.14.2. Ethernet PCS Bypass Mode 3.14.3. Ethernet PCS Run-Time Switching
3.15. CPU Interface to CPRI Intel® FPGA IP Registers x
3.15.1. CPU Interface Signals 3.15.2. Accessing the Hyperframe Control Words
3.15.2. Accessing the Hyperframe Control Words x
3.15.2.1. Specifying the Control Word 3.15.2.2. Specifying the Position in the Control Word 3.15.2.3. Retrieving the Hyperframe Control Words 3.15.2.4. Writing the Hyperframe Control Words
3.17. Extended Delay Measurement x
3.17.1. Extended Delay Measurement for Soft Internal Buffers M/N Ratio Selection Extended Delay Measurement Calculation Example 3.17.2. Extended Delay Measurement for Intel® Stratix® 10 Hard FIFOs 3.17.3. Extended Delay Measurement Interface
3.18. Deterministic Latency and Delay Measurement and Calibration x
3.18.1. Delay Measurement and Calibration Features 3.18.2. Delay Requirements 3.18.3. Single-Hop Delay Measurement 3.18.4. Multi-Hop Delay Measurement 3.18.5. Delay Calibration Features
3.18.3. Single-Hop Delay Measurement x
3.18.3.1. Rx Path Delay 3.18.3.2. Tx Path Delay 3.18.3.3. Round-Trip Delay
3.18.5. Delay Calibration Features x
3.18.5.1. Single-Trip Delay Calibration 3.18.5.2. Round-Trip Delay Calibration 3.18.5.3. Tx Bitslip Delay
3.18.5.1. Single-Trip Delay Calibration x
3.18.5.1.1. Single-Trip Latency Measurement and Calibration Interface Signals
3.19. CPRI Intel® FPGA IP Transceiver and Transceiver Management Interfaces x
3.19.1. CPRI Link 3.19.2. Main Transceiver Clock and Reset Signals 3.19.3. Arria V, Arria V GZ, Cyclone V, and Stratix V Transceiver Reconfiguration Interface 3.19.4. Intel® Arria® 10, Intel® Stratix® 10, and Intel Agilex® 7 Transceiver Reconfiguration Interface 3.19.5. RS-FEC Interface 3.19.6. Interface to the External Reset Controller 3.19.7. Interface to the External PLL 3.19.8. Transceiver Debug Interface
3.20. Testing Features x
3.20.1. CPRI Intel® FPGA IP Core Loopback Modes 3.20.2. CPRI Intel® FPGA IP Core Self-Synchronization Feature
4. CPRI Intel® FPGA IP Core Signals x
4.1. CPRI Intel® FPGA IP Core L2 Interface 4.2. CPRI Intel® FPGA IP Core L1 Direct Access Interfaces 4.3. CPRI Intel® FPGA IP Core Management Interfaces 4.4. CPRI Intel® FPGA IP Core Transceiver and Transceiver Management Signals
1. About the CPRI Intel® FPGA IP Core
2. Getting Started with the CPRI Intel® FPGA IP Core
3. Functional Description
4. CPRI Intel® FPGA IP Core Signals
5. CPRI Intel® FPGA IP Core Registers
6. CPRI Intel® FPGA IP User Guide Archives
7. Document Revision History for the CPRI Intel® FPGA IP User Guide

3.17.1. Extended Delay Measurement for Soft Internal Buffers

The CPRI Intel® FPGA IP uses a dedicated clock, ex_delay_clk, to measure the delay through the RX and TX internal buffers to your desired precision. The extended delay process is identical for the two directions of flow through the IP core; the TX_EX_DELAY and RX_EX_DELAY registers hold the same information for the two directions.

The tx_msrm_period field of the TX_EX_DELAY register contains the value N, such that N clock periods of the ex_delay_clk clock are equal to some whole number M of cpri_clkout periods. For example, N may be a multiple of M, or the M/N frequency ratio may be slightly greater than 1, such as 64/63 or 128/127. The application layer specifies N to ensure the accuracy your application requires. The accuracy of the Tx buffer delay measurement is N/least_common_multiple(N,M) cpri_clkout periods.

Similarly, the rx_msrm_period field of the RX_EX_DELAY register contains the value N, such that N clock periods of the ex_delay_clk clock are equal to some whole number M of cpri_clkout periods.

If your application does not require this precision, drive the ex_delay_clk input port with the cpri_clkout signal. In this case, the M/N ratio is 1 because the frequencies are the same.

The tx_buf_delay field of the TX_DELAY register indicates the number of 32-bit words currently in the Tx buffer. After you program the tx_msrm_period field of the TX_EX_DELAY register with the value of N, the tx_ex_delay field of the TX_EX_DELAY register holds the current measured delay through the Tx buffer. The unit of measurement is cpri_clkout periods. The tx_ex_delay_valid field indicates that a new measurement has been written to the tx_ex_delay field since the previous register read. The following sections explain how you set and use these register values to derive the extended Tx delay measurement information.

M/N Ratio Selection

As your selected M/N ratio approaches 1, the accuracy provided by the extended delay measurement increases.

Table 40.  Resolution as a Function of M/N Ratio at 3.072 Gbps
M N cpri_clkout Period ex_delay_clk Period Resolution
128 127 13.02 ns (1/76.80 MHz) 13.12 ns ±100 ps
64 63 13.22 ns ±200 ps
1 4 3.25 ns ±3.25 ns

Extended Delay Measurement Calculation Example

This section walks you through an example that shows you how to calculate the frequency at which to run ex_delay_clk, and how to program and use the registers to determine the delay through the CPRI Receive Buffer.

For example, assume your CPRI Intel® FPGA IP runs at CPRI line bit rate 3.072 Gbps. In this case, the cpri_clkout frequency is 76.80, so a cpri_clkout cycle is 1/76.80 MHz.

If your accuracy resolution requirements are satisfied by an M/N ratio of 128/127, perform the following steps:

  1. Program the value N=127 in the rx_msrm_period field of the RX_EX_DELAY register at offset 0x54.
  2. Perform the following calculation to determine the ex_delay_clk frequency that supports your desired accuracy resolution:

    ex_delay_clk period = (M/N) cpri_clkout period = (128/127)(1/(76.80 MHz)= 13.123356 ns.

    Based on this calculation, the frequency of ex_delay_clk is 1/(13.123356 ns)

    The following steps assume that you run ex_delay_clk at this frequency.

  3. Read the value of the RX_EX_DELAY register at offset 0x54.

    If the rx_ex_delay_valid field of the register is set to 1, the value in the rx_ex_delay field has been updated, and you can use it in the following calculations. For this example, assume the value read from the rx_ex_delay field is 0x107D, which is decimal 4221.

  4. Perform the following calculation to determine the delay through the Rx buffer:

    Delay through Rx buffer = (rx_ex_delay x cpri_clkout period) / N = (4221 x 13.02083 ns) / 127 = 432.7632 ns.

    This delay comprises (432.7632ns / 13 .02083 ns) = 33.236 cpri_clkout clock cycles.

These numbers provide you the result for this particular example. For illustration, the preceding calculation shows the result in nanoseconds. You can derive the result in cpri_clkout clock cycles by dividing the preceding result by the cpri_clkout clock period. Alternatively, you can calculate the number of cpri_clkout clock cycles of delay through the Rx buffer directly, as rx_msrm_period/N.

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