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AR# 63960

FIFO Generator v12.0 - [Common 17-55] 'get_property' expects at least one object.[axis_fifo_32x16_clocks.xdc]


I am using the FIFO Generator, and receive the following Critical Warning during implementation, and when I open a Synthesized design.

This occurs in the example design as well.

[Common 17-55] 'get_property' expects at least one object.[axis_fifo_32x16_clocks.xdc]

What can cause this problem and how can I avoid it?


This is a known issue in FIFO Generator.

The Critical Warning is caused by the following constraints:

set wr_clock [get_clocks -of_objects [get_ports s_aclk]]
set rd_clock [get_clocks -of_objects [get_ports m_aclk]]

The constraints expect clocks signals in the get_clocks command.

You will need to create clocks for them before you use get_clocks.

For example:

create_clock -period 10.000 -name s_aclk -waveform {2.000 7.000} [get_ports s_aclk]
create_clock -period 20.000 -name m_aclk -waveform {2.000 12.000} [get_ports m_aclk]

After this, you can double check whether they are considered clock signals by using following command:


Then reset all of the runs and the issue will be solved.

AR# 63960
Date Created 03/19/2015
Last Updated 05/29/2015
Status Active
Type General Article
  • FIFO Generator