V-Series Transceiver PHY IP Core User Guide

ID 683171
Date 7/26/2022
Public
Document Table of Contents

16.8. SDC Timing Constraints

This section describes SDC timing constraints for the Cyclone V Native PHY.

The Intel® Quartus® Prime software reports timing violations for asynchronous inputs to the Standard PCS. Because many violations are for asynchronous paths, they do not represent actual timing failures. You may choose one of the following three approaches to identify these false timing paths to the Intel® Quartus® Prime or TimeQuest software.

  • You can cut these paths in your Synopsys Design Constraints (.sdc) file by using the set_false_path command as shown in the following example.

Using the set_false_path Constraint to Identify Asynchronous Inputs

set_false_path -through {*8gbitslip*} -to  [get_registers *8g_rx_pcs*SYNC_DATA_REG*]
set_false_path -through {*8gbytordpld*} -to [get_registers *8g_rx_pcs*SYNC_DATA_REG*] 
set_false_path -through {*8gcmpfifoburst*} -to [get_registers *8g_rx_pcs*SYNC_DATA_REG*] 
set_false_path -through {*8gphfifoburstrx*} -to [get_registers *8g_rx_pcs*SYNC_DATA_REG*] 

set_false_path -through {*8gsyncsmen*} -to [get_registers *8g*pcs*SYNC_DATA_REG*]
set_false_path -through {*8gwrdisablerx*} -to [get_registers *8g_rx_pcs*SYNC_DATA_REG*] 
set_false_path -through {*rxpolarity*} -to [get_registers *SYNC_DATA_REG*]
set_false_path -through {*pldeidleinfersel*} -to [get_registers *SYNC_DATA_REG*]
  • You can use the set_max_delay constraint on a given path to create a constraint for asynchronous signals that do not have a specific clock relationship but require a maximum path delay.

Using the max_delay Constraint to Identify Asynchronous Inputs

# Example: Apply 10ns max delay
set_max_delay -from *tx_from_fifo* -to *8g*pcs*SYNC_DATA_REG1 10
  • You can use the set_false path command only during Timequest timing analysis.

Using the set_false TimeQuest Constraint to Identify Asynchronous Inputs

#if {$::TimeQuestInfo(nameofexecutable) eq "quartus_fit"} { 
#} else {
#set_false_path -from [get_registers {*tx_from_fifo*}] -through {*txbursten*} -to [get_registers *8g_*_pcs*SYNC_DATA_REG
Note: In all of these examples, you must substitute your actual signal names for the signal names shown.

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