Other Minor Differences; Termination; Crc; Loopback - Xilinx Virtex-5 RocketIO GTP User Manual

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Other Minor Differences

Termination

In Virtex-II Pro devices, the transceivers contain on-chip termination and reference
voltages for VTTX and VTRX. In Virtex-4 devices, the MGTs use a reference resistor to
create the termination circuitry for each MGT column. The Virtex-5 GTP transceiver
simplifies the termination circuitry by providing a calibrated 50Ω termination.
shows the termination options for each FPGA generation.
Table A-8: Termination Options

CRC

CRC support has changed over the generations of transceivers.
support provided by all four transceiver families.
Table A-9: CRC Transceiver Support

Loopback

The loopback options of the Virtex transceivers have evolved to improve flexibility.
Virtex-II Pro MGTs have two loopback modes, and Virtex-4 MGTs have four loopback
modes.
Table A-10: Loopback Options
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Termination Virtex-II Pro MGT
50/75 Ω
Value
Voltage Pins VTTX/VTRX
Virtex-II Pro Virtex-4
MGT
CRC-32 Independent CRC-32
block supports datapath
from 8 to 64 bits wide.
Table A-10 shows this evolution.
Mode
Parallel Loopback (Tx → RX)
Serial Pre-Driver
Serial Post-Driver
Serial Digital Receiver
External Data PMA-Only Parallel
Loopback
PCI Express Repeater
www.xilinx.com
Virtex-4 MGT
50Ω
VTTX/VTRX
MGT
Independent CRC block supports two CRC-32
calculations over 32-bit datapaths or a single
CRC-32 calculation over a 64-bit datapath.
Virtex-II Pro
MGT
Yes
–
Yes
–
–
–
Other Minor Differences
Table A-8
Virtex-5 GTP
Transceiver
50Ω
MGTAVTTTX/MGTAVTTRX
Table A-9 shows the CRC
Virtex-5
GTP Transceiver
Virtex-4 Virtex-5 GTP
MGT Transceiver
Yes Yes
Yes Yes
– –
Yes –
– Yes
– Yes
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