AR# 5918: 1.5i Timing - PAR appears to hang due to problem with OFFSET constraint.
AR# 5918
1.5i Timing - PAR appears to hang due to problem with OFFSET constraint.
説明
KEYWORDS: PAR, hang, xla, rpm
URGENCY: hot
GENERAL DESCRIPTION: PAR and other applications doing timing analysis may appear to be hung when an OFFSET constraint is evaluated against and INFF residing in the same clock IOB as the intended clock network.
ソリューション
The incorrect timing behavior results because a buffer and FF is used in the same clock IOB. This can be avoided by moving the FF out of the clock IOB.
In schematic, instead of using the IFD component, use the IBUF and FD component.
In HDL, in the Constraints Editor, for the impeding clock signal, select IOB reg = FALSE.
A software fix for this problem will be available in the 2.1i release due to be shipped in June, 1999.