Gigabit Transceivers

Access to 28 high-speed serial transceiver pairs (28 Rx and 28 Tx) corresponding to 5 GTH quads (224, 225, 226, 227 and 228) and 2 GTY quads (129 and 130) on the FPGA are available on the expansion connectors. The MGTREFCLK 0 for every transceiver quad is also routed to the associated expansion connector. For full connection details see the XEM8370 Pin List.

MGT QuadFPGA Supported Bitrate (-1 speed)
GTY 12916.3 Gbps
GTY 13016.3 Gbps
GTH 22412.5 Gbps
GTH 22512.5 Gbps
GTH 22612.5 Gbps
GTH 22712.5 Gbps
GTH 22812.5 Gbps


0.01μF AC-coupling capacitors are installed between the expansion connectors and the FPGA for all MGTREFCLK signals.

AC-coupling capacitors are not installed for any of the transceiver transmit or receive pairs. If AC-coupling is desired or required for the serial application, they should be installed on the peripheral side (your board).

IBERT Configuration

AMD provides the IBERT tool to test and experiment with gigabit transceivers. Appropriate MGTREFCLK’s must be supplied to the GTY and GTH banks through the expansion connectors. The settings below are compatible with the XEM8370 using Vivado 2022.2:

ProtocolCustom 1 
Line RateGTY: 16.3 Gbps GTH: 12.5 Gbps 
Data Width40 
Ref Clk100.000 MHz 
Quad Count7 
GTX LocationProtocol SelectedRefclk Selection
QUAD_129Custom 1 / 16.3GbpsMGTREFCLK0_129
QUAD_130Custom 1 / 16.3GbpsMGTREFCLK0_129
QUAD_224Custom 1 / 12.5GbpsMGTREFCLK0_226
QUAD_225Custom 1 / 12.5GbpsMGTREFCLK0_226
QUAD_226Custom 1 / 12.5GbpsMGTREFCLK0_226
QUAD_227Custom 1 / 12.5GbpsMGTREFCLK0_226
QUAD_228Custom 1 / 12.5GbpsMGTREFCLK0_226
Add RXOUTCLK ProbesUnchecked 
Clock TypeSystem Clock 
I/O StandardLVDS 
P Package PinE22 
Frequency100 MHz 
Enable DIFF Term.Unchecked 

Gigabit Transceiver IBERT Performance

AMD’s IBERT tool enables an automated self-measurement of a GTH channel’s eye diagram when used in a loopback mode. Eye diagrams for two different speeds were captured using this tool with a simple loopback peripheral attached to the expansion headers. While results may vary, these are typical captures and actually represent the worst case capture over all channels for the respective rates.

Note that in loopback modes, it can be helpful to disable the GBT DFE (decision feedback equalizer) to avoid over-compensation. The TX Diff Swing must also be set so that it does not over saturate the receiver.

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