Device Family: Arria® V, Arria® V GT, Arria® V ST

Type: Answers

Area: Component, HSIO

Why might the PCI Express signal detect feature fail at low temperatures on Arria V GT and ST devices and the link fail to train?


Due to an incorrect receiver common mode voltage (Rx Vcm) setting in Quartus® II software version 14.0 and earlier, the PCI Express® signal detect feature may fail at low temperatures on Arria® V GT and ST devices and the link fail to train.

The table below shows the Arria device VCCR_GXB and Rx Vcm requirements.

Device VCCR_GXB Voltage Rx Vcm Voltage
Arria V GX, SX 1.1V/1.15V 0.65V
Arria V GT, ST 1.2V 0.75V


To work around this problem in Arria V GT and ST devices you can download and install the patch below and add the following Quartus II Settings File (QSF) assignment for all PCI Express receiver channels in your design.

set_instance_assignment -name XCVR_RX_COMMON_MODE_VOLTAGE VTT_0P75V -to <pin_name>

You must make the above assignment to all PCI Express receiver pins in your design and you should not use wildcard characters (*) in your assignments.

This problem will be fixed in a future version of the Quartus II software.