General Description: The timing report (trce -a) in 4.1i software with Service Pack 2 or Service Pack 3 for a Virtex-E design incorrectly assumes that the data sheet values can be used. However, this is not the case when neither a DLL nor an IOB delay element are used, or when both a DLL and a delay element are used.
The data sheet numbers should only be used when:
- A delay element is used but no DLL is used, or - When a DLL is used but no delay element is used.
How do I find the correct setup/hold values?
The easiest way to solve this problem is to disable the delay element being used with the DLL, or to enable a delay element when a DLL is not being used. This will allow the correct setup/hold numbers to be reported, and a zero hold time will also be guaranteed.
This issue will be fixed in a future version of the timing software.
Timing reports generated before 4.1i are correct. The pin to pin numbers were not introduced until version 4.1i for Virtex-E.
Use the 3.3i analyzed results in order to get the correct timing numbers. The speed files have not changed the setup/hold values or the global clock tree for Virtex-E since version 3.3i. Thus, the timing numbers used in the 3.3i software will be nearly identical to those of the 4.1i software.