Type: Answers

Area: Intellectual Property


IP Product: Triple Speed Ethernet MAC

Why do I see warnings in TimeQuest related to my Triple Speed Ethernet (TSE) sdc file after sourcing the TSE clocks from internal user logic rather than device input pins?

Description

This problem is due to limitations within the TSE sdc file which relies on the assumption that the TSE clocks are sourced by top level pins rather than internal logic.

Workaround/Fix

For cases where your TSE clocks are sourced from internal logic for which a create_clock or create_generated_clock assignment already exists then you are required to modify the TSE sdc file to remove the clock assignments for these clocks.

For Example:

In the case where the TSE input clock "clk" is fed by an internal PLL rather than a top level clock pin then you would receive a warning such as the one below during timing analysis:

Warning: Ignored filter at tse_constraints.sdc(363): clk could not be matched with a port

**Note that the line number may be different depending on the configuration of your TSE core.

The reason for the warning is that the TSE sdc file contains a create_clock assignment for the "clk" input which is no longer required as the "clk" port of the TSE core is now fed from a PLL output which is already constrained.

To avoid the warning simply comment out the create_clock constraint as it is not required.

The solution above applies to any TSE clock which is fed from internal logic rather than a top level pin.

This limitation is scheduled to be resolved in a future release of the Triple Speed Ethernet IP.