AR# 13480

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4.2i Timing Analyzer/Virtex-E Speed Files - Incorrect guaranteed setup and hold times are reported for Virtex-E for uncommon IOB configurations, Tiockp

Description

Keywords: 4.1i, 4.2i, Timing, Analyzer, speedfiles, setup, hold, offset, Virtex

Urgency: Standard

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?

Solution

1

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.

2

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.
AR# 13480
Date 08/12/2003
Status Archive
Type General Article
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