How do I verify the correct frequency of divfwdclk when an incorrect frequency of divfwdclk is shown in the Quartus Prime TimeQuest Timing Report?

Description

The frequency of divfwdclk  shown in Quartus® Prime TimeQuest timing report for certain combinations of data rate and SERDES factor in Stratix® V devices may be incorrect. For example:

Enable Dynamic Phase Alignment

Deserialization factor = 10

Input date rate = 150Mpbs

Input clock frequency = 150Mhz

DPA mode : use divfwdclk

The divfwdclk should be 150MHz/10 = 15MHz, but TimeQuest reports a divfwdclk of 30MHz.

Resolution

To work around this issue, use the create generated clock command in a user SDC file or in the TimeQuest Timing Analyzer to divide the divfwdclk to the correct frequency. For example:

create_generated_clock -name divfwdclk -source [get_pins {rx_cmp_inst|ALTLVDS_RX_component|auto_generated|rx_0|dpaclkin[0]}] -divide_by 2 [get_pins {rx_cmp_inst|ALTLVDS_RX_component|auto_generated|rx_0|divfwdclk}]