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AR# 6066

2.1i: RISING and FALLING constraint grouping does not filter out non-FF elements


Keywords: timing constraints, Rising, Falling, clock sense, two
phase clock, 2 phase clock, 1.5i

Urgency: Standard

General Description:
The RISING and FALLING constraint syntax only looks at the
rising or falling edge flip flops in that time group. The time group may
have other synchronous elements like RAMs or Latches, but the
RISING or FALLING time group should only include the Flip Flops
from that time group. The Problem is that the timing group contains
the rising or falling edge flip flops, along with other synchronous
elements (Rams, Latches) will be placed within the time group.

The Development System Reference Guide documentation, Chapter 4
states that the timing group(RISING or FALLING) must be a group that
includes only flip-flops.


Create a time group of only flip flops.

TIMEGROUP my_timing_grp_rising_FFS = RISING my_timing_grp FFS;

Please consult Chapter 4 of the Development System Reference Guide
for more information on creating timing groups and predefined
AR# 6066
Date Created 03/31/1999
Last Updated 07/10/2001
Status Archive
Type General Article