Description

General Description: What should a user look for when setting the startup sequence to wait for DLL lock?

Solution

Two things must be done to make sure the device waits for the DLL's to lock:

1) Put the STARTUP_WAIT = TRUE property in the UCF file or in the code for each appropriate DLL.

2) Set the Lck_cycle to something other than NoWait. This can be done in the configuration templates if you are using the GUI (either Foundation or Design Manager) or with -g Lck_cycle:chosencycle if command line is used.

The lck_cycle can be set to a startup phase before DONE, GWE, GTS, or GSR are triggered if there is no board-level deskew happening. GTS controls the global tri-state, which will disable all outputs. Inputs are valid, but if outputs are required for the DLL to lock, the device will never configure in this situation. If that is a problem, set lck_cycle to a phase after GTS is de-asserted.