Frequency of coreclkout Reported Incorrectly for Stratix V Hard IP for PCI Express IP Core when the ATX PLL is Used

Description

The frequency of coreclkout is reported incorrectly for the Stratix V Hard IP for PCI Express IP Core when the ATX PLL is used in Gen1 devices. The Quartus II software reports a frequency for coreclkout that is one half the actual frequency.

Resolution

The workaround is to add the following Synopsys Design Constraint (SDC) for coreclkout:

create_clock -period <half of the Timequest-reported period> [get_pins {*|altpcie_hip_256_pipen1b|stratixv_hssi_gen3_pcie_hip|observablecoreclkdiv}]

For example, if TimeQuest reports a 16 ns clock, the SDC is:

create_clock -period 8.000 [get_pins {*|altpcie_hip_256_pipen1b|stratixv_hssi_gen3_pcie_hip|observablecoreclkdiv}]