2.8.1. Reducing the DCFIFO Depth - 2025-12-16

Stratix 10 Embedded Memory User Guide
Version
24.2

You can change the DCFIFO depth manually in the RAM IP Parameter Editor. Reducing the DCFIFO depth can improve setup timing slacks when you see multiple setup timing violations in the DCFIFO used in the emulated true dual-port (TDP) RAM in Stratix® 10 devices.

  1. On the Project Navigator Hierarchy tab, expand your design hierarchy and take note of the entity names of the following instances under the emulated TDP RAM instance:
    1. Navigate to ram_2port_0 > fifo_wrapper_in > dcfifo_in and take note of the entity name of the dcfifo_in instance.
    2. Navigate to ram_2port_0 > fifo_wrapper_out > dcfifo_out and take note of the entity name of the dcfifo_out.
    Figure 18. Example of dcfifo_in and dcfifo_out Entity Names in the Hierarchy Tab
  2. On the Project Navigator Files tab, expand the .ip file of the emulated TDP RAM and locate <entity name of dcfifo_in>.v and <entity name of dcfifo_out>.v files.
    Figure 19. Examples of .ip Files in the Files Tab
  3. Click on the <entity names of the dcfifo_in>.v file and find the following parameters in the defparam declarations:
    • dcfifo_component.lpm_numwords = <lpm_numwords value>
    • dcfifo_component.lpm_widthu = <lpm_widthu value>
  4. Change the value of dcfifo_component.lpm_numwords and dcfifo_component.lpm_widthu.
    • The value of dcfifo_component.lpm_numwords must be greater than the value of the clock frequency ratio of clock B (fast clock) divided by clock A (slow clock) of the emulated TDP RAM IP.
    • The value of the dcfifo_component.lpm_numwords must be greater than 4.
    • The value of dcfifo_component.lpm_numwords must be the value of 2^dcfifo_component.lpm_widthu. For example:
      • If the ratio of the clock B frequency/clock A frequency is 5, the minimum dcfifo_component.lpm_numword must be 8 (2^3).
      • If the dcfifo_component.lpm_numword is 8 (2^3), then the value of dcfifo_component.lpm_widthu is 3.
  5. Save the file. Repeat the same steps for <entity names of the dcfifo_out>.v file of the emulated TDP RAM.
Note: If the emulated TDP RAM IP is regenerated, the above files are regenerated and the parameter values are restored to their default values.