AR# 7197

描述

Problem Description:

In M1.5i, when the following timing constraints are entered in the UCF or NCF file, they

are not written correctly into the PCF file.

NET clka TNM_NET = A;

NET clkb TNM_NET = B;

TIMESPEC TS1 = PERIOD A 100 Mhz;

TIMESPEC TS2 = PERIOD B TS1/2;

These timespecs would become the following in the PCF file in M1.5i:

TS1 = PERIOD A 10 ns;

TS2 = PERIOD B TS1/2;

Note that TS2 should have been 50 Mhz(20ns), however it's getting written

as 5 nS.

In 2.1i, the correct Timespecs are written in the PCF file:

TS1 = PERIOD A 10 ns;

TS2 = PERIOD B TS1 * 2;

解决方案

Due to the changes in 2.1i, the existing m1.5i timespecs will give you

the wrong behavior in 2.1i. The users only need to make appropriate

changes in the UCF file to compenstate this problem.

This problem only exists when the Keyword PERIOD is used. A FROM-TO

spec in terms of frequency has always been handled properly, and base specs

in terms of delays do not cause problems.