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AR# 3821

Foundation, MAP: Excessive logic removed (trimmed) from a design captured in Foundation schematic.

Description

KEYWORDS: ngdbuild, map, removed, trimmed, stripped, foundation, terminal, IPAD

URGENCY: Standard

GENERAL DESCRIPTION:
Excess logic can get stripped from a design if a customer uses I/O terminals to
define top-level I/O on a schematic rather than using IPADs and OPADs from the
Xilinx Unified Libraries.

The stripping actually only occurs on the clock buffers. In the trimming section of
the Map Report the clocks will be defined as sourceless.

This occurs because ngdbuild will automatically insert IPADs in front of IBUFs, even if these IPADs do not exist in the EDIF netlist.



解决方案

The resolution is to always use IPADs and OPADs, and not I/O terminals to represent the pins of a Xilinx device. I/O terminals should ONLY be used to make
connections between levels of hierarchy.

Note: In F1.5, I/O terminals have been renamed to Hierarchy Connectors to help
alleviate inappropriate use of them.
AR# 3821
创建日期 04/24/1998
Last Updated 08/16/2002
状态 Archive
Type 综合文章