The Quartus® II software version 13.0sp1 and earlier have incorrect settings for the Receiver Common Mode Voltage (Vcm) and the Receiver Signal Detection Voltage Threshold (Vth) for the Cyclone® V PCI Express® Hard IP core. This may cause the PCIe® link to not link train or link up to the maximum lane width.
1) Add the following INI variables to a quartus.ini file to enable manual QSF settings for Vcm and Vth.
ignore_cv_sd_threshold_rule = on
ignore_cv_sd_vcm_sel_rule = on
2) Place this quartus.ini file in the following directory:
<Working_Directory>/
3) Set the Vcm to 0.65V by adding the following QSF assignment:
set_instance_assignment -name XCVR_RX_COMMON_MODE_VOLTAGE VTT_0P65V -to <your_rx_pin_names>
4) Set the Vth.
• If VCCR/VCCT_GXB is 1.1V, set the Vth to 35mV by adding the following QSF assignment:
set_instance_assignment -name XCVR_RX_SD_THRESHOLD 4 -to <your_rx_pin_names>
• If VCCR/VCCT_GXB is 1.2V, set the Vth to 30mV by adding the following QSF assignment:
set_instance_assignment -name XCVR_RX_SD_THRESHOLD 3 -to <your_rx_pin_names>