CPLL Clocking - 2.0 English

PG289 SMPTE UHD-SDI TX Subsystem

Document ID
PG289
Release Date
2022-05-18
Version
2.0 English

Note: For Versal® ACAP GT clocking information, refer to the Versal ACAP GTY Transceivers Architecture Manual [Ref 18] .

The following figure shows the UltraScale GT clocking architecture.

Figure 3-1: GT Clocking Architecture in Loopback Example Design

X-Ref Target - Figure 3-1

CPLL_Recommendation.jpg

Two reference clocks are used to support integer and fractional line rates of SDI. The reference clock for QPLL0 is fixed to 297 MHz from the on-board Si570 chip. The reference clock for the CPLL is fixed at 296.7 MHz from Si5328 chip output. The CPLL switches between the 297 MHz and the 296.7 MHz reference clocks using the CPLLREFCLKSEL.

IMPORTANT: When using QPLL0 and QPLL1 for 12G-SDI integer and fractional (1/1.001) rate change, switching between rates on the SDI-RX can introduce a glitch on the clock which in turn introduces CRC errors on the TX channel. CRC errors do not occur in SD-SDI/HD-SDI/3-G SDI/6-G SDI integer/fractional modes with QPLL0 and QPLL1 clocking combination. For more information, see Answer Records 72254 and 72449 . Therefore, it is not recommended to use this clocking configuration when both transmit and receive 12G-SDI integer and fractional modes use the same transceiver. If required, Xilinx recommends to use a CPLL-QPLL combination with CPLL for TX and QPLL0/1 for RX as shown in This Figure .

The integer and fractional rates for TX can be selected using a CPLL reference clock input selection with 297 MHz and 296.7 MHz respectively. This CPLL/QPLL clocking combination is not feasible with -1 speed grade devices because CPLL does not support 12G-SDI line rates. You need to select an UltraScale+™ GTH/GTY -2 speed grade or faster rate with >0.85V. Refer to the respective FPGA device data sheets for CPLL line rate limits. The UHD-SDI example designs are updated to use the CPLL and QPLL clocking combination. The UHD-SDI GT IP is updated to provide CPLL support from version 2019.2 or later.

Note: For more information refer to PG290 (KCU116 Example design section) [Ref 10] .