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2.1. Installation and Licensing
2.2. Generating aCPRI Intel® FPGA IP
2.3. CPRI Intel® FPGA IP Generated Files
2.4. CPRI Intel® FPGA IP Parameters
2.5. Integrating the CPRI IP into your Design: Required External Blocks
2.6. Simulating Intel FPGA IP Cores
2.7. Running the CPRI IP Design Example
2.8. CPRI Design Example Clocks
2.9. About the Testbench
2.10. Compiling the Full Design and Programming the FPGA
2.5.1. Adding the Transceiver TX PLL IP Core
2.5.2. Adding the Reset Controller
2.5.3. Adding the Transceiver Reconfiguration Controller
2.5.4. Adding the Off-Chip Clean-Up PLL
2.5.5. Adding and Connecting the Single-Trip Delay Calibration Blocks
2.5.6. CPRI IP Transceiver PLL Calibration
2.5.7. Reference and System PLL Clock for your IP Design
3.1. Interfaces Overview
3.2. CPRI Intel® FPGA IP 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
3.19.1. 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. Arria® 10, Stratix® 10, and 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
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3.18.3.3. Round-Trip Delay
You can read the ROUND_TRIP_DELAY register or calculate the round-trip delay from the delay components (Rx path delay, Tx path delay,cable delay, and Rx-to-Tx switching latency). The round_trip_delay field of the ROUND_TRIP_DELAY register in an REC master records the total round-trip delay from the start of the internal transmit radio frame in the REC to the start of the internal receive radio frame in the REC, that is, from SAP to SAP, in CPRI REC and RE masters.
CPRI v7.0 Specification requirements R-20 and R-21 address the round-trip delay. Requirement R-20 addresses the measurement without including the cable delay, and requirement R-21 is the requirement for the cable delay. Both requirements state that the variation must be no more than ±16.276 ns.
To monitor the round-trip delay, you must check periodically to confirm that the variation in measurements over time is small enough that the requirements are met.
Note: The round trip delay is the sum of the Tx path delays through the REC master and the RE slave, the Rx path delays through the REC master and the RE slave, the cable delay, and the Tx-to-Rx switching delay, sometimes referred to as the loopback delay. The Tx-to-Rx switching delay is labeled T_S_Rx_Tx in the figure. The Tx-to-Rx switching delay depends on the loopback path and the device.