330 www.xilinx.com Virtex-4 RocketIO MGT User GuideUG076 (v4.1) November 2, 2008Appendix E: Virtex-II Pro/Virtex-II Pro X to Virtex-4 RocketIO Transceiver Design Migration R.CRCCRC support has changed over the three generations of transceivers. Table E-7 shows theCRC support for all three transceiver families.LoopbackLoopback support has changed over the three generations of transceivers. In Virtex-II Protransceivers, there were two loopback modes. Table E-8 shows the various loopbackmodes for all the three transceiver families.SerializationAs in Virtex-II Pro X devices, Virtex-4 also serializes and sends the least significant bytefirst. This is opposite of the format Virtex-II Pro devices used in sending the mostsignificant byte first.Table E-6: Termination OptionsTermination Virtex-II Pro Virtex-II Pro X Virtex-4Value 50/75Ω 50Ω 50ΩVoltage Pins VTTX /V TRX VTTX /V TRX VTTX /VTRXTable E-7: CRC Transceiver SupportVirtex-II Pro Virtex-II Pro X Virtex-432-bit CRC CRC must be done in fabric.Flexible and independentCRC from 8 to 64 bits widewith the 32-bit CRCpolynomial.Table E-8: Loopback OptionsMode Virtex-II Pro Virtex-II Pro X Virtex-4Parallel Loopback (Tx →RX) Yes Yes YesSerial Pre-Driver – Yes YesSerial Post-Driver Yes Yes –
